WAVELENGTH COMBINER PHOTONIC INTEGRATED CIRCUIT WITH GRATING COUPLING OF LASERS
Systems, devices, and methods of manufacturing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. Generally, the optical engines of the present disclosure integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. Photonic integrated circuits having grating couplers thereon may be used to wavelength multiplex beams of light emitted by the plurality of laser diodes into a coaxially superimposed aggregate beam. Such optical engines may have various advantages over existing designs including, for example, smaller volumes, better manufacturability, faster modulation speed, etc. WHUDs that employ such optical engines and laser projectors are also described.
The present disclosure is generally directed to systems, devices, and methods relating to optical engines, for example, optical engines for laser projectors used in wearable heads-up displays or other applications.
Description of the Related ArtA projector is an optical device that projects or shines a pattern of light onto another object (e.g., onto a surface of another object, such as onto a projection screen) in order to display an image or video on that other object. A projector necessarily includes a light source, and a laser projector is a projector for which the light source comprises at least one laser. The at least one laser is temporally modulated to provide a pattern of laser light and usually at least one controllable mirror is used to spatially distribute the modulated pattern of laser light over a two-dimensional area of another object. The spatial distribution of the modulated pattern of laser light produces an image at or on the other object. In conventional scanning laser projectors, at least one controllable mirror may be used to control the spatial distribution, and may include: a single digital micromirror (e.g., a microelectromechanical system (“MEMS”) based digital micromirror) that is controllably rotatable or deformable in two dimensions, or two digital micromirrors that are each controllably rotatable or deformable about a respective dimension, or a digital light processing (“DLP”) chip comprising an array of digital micromirrors.
In a conventional laser projector comprising an RGB (red/green/blue) laser module with a red laser diode, a green laser diode, and a blue laser diode, each respective laser diode may have a corresponding respective focusing lens. Each of the laser diodes of a laser module are typically housed in a separate package (e.g., a TO-38 package or “can”). The relative positions of the laser diodes, the focusing lenses, and the at least one controllable mirror are all tuned and aligned so that each laser beam impinges on the at least one controllable mirror with substantially the same spot size and with substantially the same rate of convergence (so that all laser beams will continue to have substantially the same spot size as they propagate away from the laser projector towards, e.g., a projection screen). In a conventional laser projector, it is usually possible to come up with such a configuration for all these elements because the overall form factor of the device is not a primary design consideration. However, in applications for which the form factor of the laser projector is an important design element, it can be very challenging to find a configuration for the laser diodes, the focusing lenses, and the at least one controllable mirror that sufficiently aligns the laser beams (at least in terms of spot size, spot position, and rate of convergence) while satisfying the form factor constraints.
A head-mounted display is an electronic device that is worn on a user's head and, when so worn, secures at least one electronic display within a viewable field of at least one of the user's eyes, regardless of the position or orientation of the user's head. A wearable heads-up display is a head-mounted display that enables the user to see displayed content but also does not prevent the user from being able to see their external environment. The “display” component of a wearable heads-up display is either transparent or at a periphery of the user's field of view so that it does not completely block the user from being able to see their external environment. A “combiner” component of a wearable heads-up display is the physical structure where display light and environmental light merge as one within the user's field of view. The combiner of a wearable heads-up display is typically transparent to environmental light but includes some optical routing mechanism to direct display light into the user's field of view.
Examples of wearable heads-up displays include: the Google Glass®, the Optinvent Ora®, the Epson Moverio®, and the Sony Glasstron®, just to name a few.
The optical performance of a wearable heads-up display is an important factor in its design. When it comes to face-worn devices, users also care a lot about aesthetics and comfort. This is clearly highlighted by the immensity of the eyeglass (including sunglass) frame industry. Independent of their performance limitations, many of the aforementioned examples of wearable heads-up displays have struggled to find traction in consumer markets because, at least in part, they lack fashion appeal or comfort. Most wearable heads-up displays presented to date employ relatively large components and, as a result, are considerably bulkier, less comfortable and less stylish than conventional eyeglass frames.
Direct Laser WritingFemtosecond laser micro-machining is a direct-laser-write and rapid prototyping technique that provides great potential for optical device fabrication. Strong focusing of femtosecond laser light into transparent glass can induce positive refractive index modifications up to 0.01 refractive index units (RIU) within the material and without surface damage. Since then, ultrafast (femto/pico-second) lasers have been shown to enable flexible 3D structuring of various glasses, and has led to the demonstration of many types of optical devices (waveguides, couplers, Bragg gratings, waveplates, etc.) that serve as building blocks for 3D optical circuits.
Direct-laser-writing uses ultrashort laser pulses to confine strong nonlinear optical interactions that may induce, for example, positive or negative refractive index changes in bulk transparent materials for creating optical waveguides (WGs). The mechanisms by which direct-laser-write modifications occur include, but are not limited to, multiphoton ionization, avalanche ionization, electron-atom collisions, plasma interactions, thermal effects (e.g. diffusion, heat accumulation), energy dissipation, and material cooling leading to inhomogeneous solidification. For direct-laser-writing waveguides, waveguide performance can be tuned and optimized by, but not limited to, the writing laser's properties (pulse duration, pulse temporal shape, bandwidth and shape, pulse repetition rate, wavelength, polarization, and beam spatial shape) and the focusing conditions (lens numerical aperture, air/liquid immersion, translation direction and speeds).
BRIEF SUMMARYAn optical engine may be summarized as including a base substrate; a plurality of laser diodes, each of the plurality of laser diodes bonded directly or indirectly to the base substrate; at least one laser diode driver circuit operatively coupled to the plurality of laser diodes to selectively drive current to the plurality of laser diodes; a cap comprising at least one wall and at least one optical window that, together with the base substrate, define an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap, and the optical window positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume; and a photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at the respective plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet.
The optical engine may further include a plurality of collimation lenses, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward to the plurality of input facets of the photonic integrated circuit. Each of the plurality of collimation lenses may be positioned within the interior volume. Each of the plurality of collimation lenses may be bonded to the optical window of the cap. The photonic integrated circuit may be bonded to the optical window of the cap.
The optical engine may further include an optical director element disposed within the interior volume, the optical director element bonded to the base substrate proximate the plurality of laser diodes, and positioned and oriented to reflect laser light from the plurality of laser diodes toward the optical window of the cap. The optical director element may include a mirror or a prism.
The optical engine may further include a collimation lens positioned and oriented to receive and collimate the aggregate beam of light from the output facet of the photonic integrated circuit. The collimation lens may include an achromatic lens. The collimation lens may include an apochromatic lens.
The optical engine may further include at least one diffractive optical element positioned and oriented to receive the aggregate beam of light, in operation, the at least one diffractive optical element provides wavelength dependent focus correction for the aggregate beam of light.
The optical engine may further include a plurality of chip submounts bonded to the base substrate, wherein each of the laser diodes are bonded to a corresponding one of the plurality of chip submounts. The plurality of laser diodes may include a red laser diode to provide a red laser light, a green laser diode to provide a green laser light, a blue laser diode to provide a blue laser light, and an infrared laser diode to provide infrared laser light. The base substrate may be formed from at least one of low temperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina, or Kovar®. The at least one laser diode driver circuit may be bonded to a first surface of the base substrate, and the plurality of laser diodes and the cap may be bonded to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. The at least one laser diode driver circuit, the plurality of laser diodes, and the cap may be bonded to a first surface of the base substrate. The plurality of laser diodes and the cap may be bonded to the base substrate, and the at least one laser diode driver circuit may be bonded to another substrate separate from the base substrate. Each of the laser diodes may include one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL). The at least one wall of the cap may include at least one continuous sidewall having a lower first end and an upper second end, the lower first end bonded to the base substrate, and the optical window may be hermetically or partially hermetically sealed to the cap proximate the upper second end.
The photonic integrated circuit may include a plurality of waveguides, each waveguide of the plurality of waveguides to receive laser light from a respective laser diode of the plurality of laser diodes. Each waveguide of the plurality of waveguides may be optimized to receive and output laser light having a wavelength corresponding to the wavelength of laser light received from the respective laser diode. The plurality of waveguides may include a waveguide combiner. The waveguide combiner may include at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Each waveguide of the plurality of waveguides may include an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing between the input facets of each waveguide. Each input facet of the plurality of input facets may be a grating input coupler. Each input facet of the plurality of input facets may be a planar region with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
A wearable heads-up display (WHUD) may be summarized as including a support structure that in use is worn on the head of a user; a laser projector carried by the support structure, the laser projector including an optical engine, including a base substrate; a plurality of laser diodes, each of the plurality of laser diodes bonded directly or indirectly to the base substrate; at least one laser diode driver circuit operatively coupled to the plurality of laser diodes to selectively drive current to the plurality of laser diodes; a cap comprising at least one wall and at least one optical window that, together with the base substrate, define an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap, and the optical window positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume; and a photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at the respective plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet; and at least one scan mirror positioned to receive the aggregate beam of light output at the output facet of the photonic integrated circuit, the at least one scan mirror controllably orientable to redirect the aggregate beam of light over a range of angles.
The WHUD may further include a processor communicatively coupled to the laser projector to modulate the generation of light signals.
The WHUD may further include a transparent combiner carried by the support structure and positioned within a field of view of the user, in operation the transparent combiner directs laser light from an output of the laser projector into the field of view of the user.
The optical engine of the WHUD may further include a collimation lens positioned and oriented to receive and collimate the aggregate beam of light from the output coupler of the photonic integrated circuit. The collimation lens may include an achromatic lens or an apochromatic lens.
The optical engine of the WHUD further may include at least one diffractive optical element positioned and oriented to receive the aggregate beam of light, in operation, the at least one diffractive optical element provides wavelength dependent focus correction for the aggregate beam of light.
The optical engine of the WHUD may further include a plurality of collimation lenses, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward to the plurality of input facets of the photonic integrated circuit. The photonic integrated circuit may be bonded to the optical window of the cap.
The optical engine of the WHUD may further include an optical director element disposed within the interior volume, the optical director element bonded to the base substrate proximate the plurality of laser diodes, and positioned and oriented to reflect laser light from the plurality of laser diodes toward the optical window of the cap. The optical engine of the WHUD may further include a plurality of chip submounts bonded to the base substrate, wherein each of the laser diodes are bonded to a corresponding one of the plurality of chip submounts. The plurality of laser diodes may include a red laser diode to provide a red laser light, a green laser diode to provide a green laser light, a blue laser diode to provide a blue laser light, and an infrared laser diode to provide infrared laser light.
The at least one laser diode driver circuit may be bonded to a first surface of the base substrate, and the plurality of laser diodes and the cap may be bonded to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. The at least one laser diode driver circuit, the plurality of laser diodes, and the cap may be bonded to a first surface of the base substrate. The plurality of laser diodes and the cap may be bonded to a first surface of the base substrate, and the at least one laser diode driver circuit may be mounted to the support structure.
Each of the laser diodes may include one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL). The at least one wall of the cap may include at least one continuous sidewall having a lower first end and an upper second end, the lower first end bonded to the base substrate, and the optical window may be hermetically or partially hermetically sealed to the cap proximate the upper second end.
The photonic integrated circuit may include a plurality of waveguides, each waveguide of the plurality of waveguides to receive laser light from a respective laser diode of the plurality of laser diodes. Each waveguide of the plurality of waveguides may be optimized to receive and output laser light having a wavelength corresponding to the wavelength of laser light received from the respective laser diode. The plurality of waveguides may include a waveguide combiner. The waveguide combiner may include at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Each waveguide of the plurality of waveguides may include an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing between the input facets of each waveguide.
Each input facet of the plurality of input facets may be a grating input coupler. Each input facet of the plurality of input facets may be a planar region with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
A laser projector may be summarized as including an optical engine, comprising: a base substrate; a plurality of laser diodes, each of the plurality of laser diodes bonded directly or indirectly to the base substrate; at least one laser diode driver circuit operatively coupled to the plurality of laser diodes to selectively drive current to the plurality of laser diodes; a cap comprising at least one wall and at least one optical window that, together with the base substrate, define an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap, and the optical window positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume; and a photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at the respective plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet; and at least one scan mirror positioned to receive the aggregate beam of light output at the output facet of the photonic integrated circuit, the at least one scan mirror controllably orientable to redirect the aggregate beam of light over a range of angles.
The laser projector may further include a processor communicatively coupled to the optical engine to modulate the generation of light signals.
The optical engine of the laser projector may further include a plurality of collimation lenses, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward to the plurality of input facets of the photonic integrated circuit. Each of the plurality of collimation lenses may be bonded to the optical window of the cap. The photonic integrated circuit may be bonded to the optical window of the cap.
The optical engine of the laser projector may further include an optical director element disposed within the interior volume, the optical director element bonded to the base substrate proximate the plurality of laser diodes, and positioned and oriented to reflect laser light from the plurality of laser diodes toward the optical window of the cap. The optical engine of the laser projector may further include a collimation lens positioned and oriented to receive and collimate the aggregate beam of light from the output facet of the photonic integrated circuit. The optical engine of the laser projector may further include at least one diffractive optical element positioned and oriented to receive the aggregate beam of light, in operation, the at least one diffractive optical element provides wavelength dependent focus correction for the aggregate beam of light.
The optical engine of the laser projector may further include a plurality of chip submounts bonded to the base substrate, wherein each of the laser diodes are bonded to a corresponding one of the plurality of chip submounts. The plurality of laser diodes may include a red laser diode to provide a red laser light, a green laser diode to provide a green laser light, a blue laser diode to provide a blue laser light, and an infrared laser diode to provide infrared laser light.
The at least one laser diode driver circuit may be bonded to a first surface of the base substrate, and the plurality of laser diodes and the cap may be bonded to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. The at least one laser diode driver circuit, the plurality of laser diodes, and the cap may be bonded to a first surface of the base substrate. The plurality of laser diodes and the cap may be bonded to the base substrate, and the at least one laser diode driver circuit may be bonded to another substrate separate from the base substrate.
Each of the laser diodes may include one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL). The at least one wall of the cap may include at least one continuous sidewall having a lower first end and an upper second end, the lower first end bonded to the base substrate, and the optical window may be hermetically or partially hermetically sealed to the cap proximate the upper second end.
The photonic integrated circuit may include a plurality of waveguides, each waveguide of the plurality of waveguides to receive laser light from a respective laser diode of the plurality of laser diodes. Each waveguide of the plurality of waveguides may be optimized to receive and output laser light having a wavelength corresponding to the wavelength of laser light received from the respective laser diode. The plurality of waveguides may include a waveguide combiner. The waveguide combiner may include at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Each waveguide of the plurality of waveguides may include an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing between the input facets of each waveguide.
Each input facet of the plurality of input facets may be a grating input coupler. Each input facet of the plurality of input facets may be a planar region with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
A method of operating an optical engine, the optical engine including a plurality of laser diodes hermetically or partially hermetically sealed in an encapsulated package, may be summarized as including causing the plurality of laser diodes to generate a corresponding plurality of beams of laser light through an optical window in the encapsulated package; coupling the plurality of beams of laser light into a respective plurality of input facets of a photonic integrated circuit; and wavelength multiplexing, by the photonic integrated circuit, the beams of laser light to generate an aggregate beam of light at an output facet of the photonic integrated circuit.
The method may further include collimating, by a collimation lens, the aggregate beam of light that exits from the output facet of the photonic integrated circuit. Collimating the aggregate beam of light may include collimating the aggregate beam of light using an achromatic lens or an apochromatic lens.
The method may further include correcting, by at least one diffractive element, wavelength dependent focus for the aggregate beam of light. Causing the plurality of laser diodes to generate laser light may include causing a red laser diode to generate red laser light, causing a green laser diode to generate green laser light, causing a blue laser diode to generate blue laser light, and causing an infrared laser diode to generate infrared laser light. Coupling the plurality of beams of laser light into a respective plurality of input facets of a photonic integrated circuit may include coupling the plurality of beams of laser light into a respective plurality of input facets of a photonic integrated circuit via a plurality of collimation lenses.
Wavelength multiplexing, by the photonic integrated circuit, the beams of laser light may include receiving, by each waveguide of a plurality of waveguides, laser light from a respective laser diode of the plurality of laser diodes, and outputting, by the plurality of waveguides, an aggregate beam of light.
The photonic integrated circuit may include a waveguide combiner which includes the plurality of input facets and the output facet, and wavelength multiplexing, by the photonic integrated circuit, the beams of laser light may include: receiving, by each input facet of the plurality of input facets, laser light from a respective laser diode of the plurality of laser diodes; and outputting, by the output facet of the waveguide combiner, a coaxially superimposed aggregate beam of light.
The photonic integrated circuit may include a plurality of waveguides, each waveguide of the plurality of waveguides including an input facet and an output facet, and wavelength multiplexing, by the photonic integrated circuit, the beams of laser light may include: receiving, by the respective input facet of each waveguide of the plurality of waveguides, laser light from a respective laser diode of the plurality of laser diodes; and outputting, by the respective output facet of each waveguide of the plurality of waveguides, a beam of light, a spacing between the output facet of each waveguide being smaller than a spacing between the input facets of each waveguide to produce an aggregate beam of light.
Coupling the plurality of beams of laser light into a respective plurality of input facets of a photonic integrated circuit may include coupling the plurality of beams of laser light into a respective plurality of grating input couplers of the photonic integrated circuit. Coupling the plurality of beams of laser light into a respective plurality of input facets of a photonic integrated circuit may include coupling the plurality of beams of laser light into the photonic integrated circuit via a plurality of planar regions with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
An optical engine may be summarized as including a base substrate; a plurality of laser diodes, each of the plurality of laser diodes bonded directly or indirectly to the base substrate; a cap comprising at least one wall that, with the base substrate, defines an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap; and a photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at respective ones of the plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet. Each of the plurality of laser diodes may be positioned immediately adjacent a respective one of the plurality of input facets of the photonic integrated circuit. Each of the plurality of input facets of the photonic integrated circuit may be positioned inside the interior volume and the at least one output facet of the photonic integrated circuit may be positioned outside of the interior volume. The cap may include at least one optical window positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume.
The photonic integrated circuit may be bonded to the optical window of the cap. The at least one wall of the cap may include at least one continuous sidewall having a lower first end and an upper second end, the lower first end bonded to the base substrate, and the optical window may be hermetically or partially hermetically sealed to the cap proximate the upper second end. The optical engine may further include an optical director element disposed within the interior volume, the optical director element bonded to the base substrate proximate the plurality of laser diodes, and positioned and oriented to reflect laser light from the plurality of laser diodes toward the optical window of the cap.
The optical engine may further include a plurality of collimation lenses, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of beams of light emitted from the plurality of laser diodes, and to output the collimated light toward to the plurality of input facets of the photonic integrated circuit. The optical engine may further include a collimation lens positioned and oriented to receive and collimate the aggregate beam of light from the output facet of the photonic integrated circuit. The optical engine may further include at least one diffractive optical element positioned and oriented to receive the aggregate beam of light, in operation, the at least one diffractive optical element provides wavelength dependent focus correction for the aggregate beam of light.
The optical engine may further include a plurality of chip submounts bonded to the base substrate, wherein each of the laser diodes are bonded to a corresponding one of the plurality of chip submounts. The plurality of laser diodes may include a red laser diode to provide a red laser light, a green laser diode to provide a green laser light, a blue laser diode to provide a blue laser light, and an infrared laser diode to provide infrared laser light.
The optical engine may further include at least one laser diode driver circuit operatively coupled to the plurality of laser diodes to selectively drive current to the plurality of laser diodes. The at least one laser diode driver circuit may be bonded to a first surface of the base substrate, and the plurality of laser diodes and the cap may be bonded to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. The at least one laser diode driver circuit, the plurality of laser diodes, and the cap may be bonded to a first surface of the base substrate. The plurality of laser diodes and the cap may be bonded to the base substrate, and the at least one laser diode driver circuit may be bonded to another substrate separate from the base substrate. Each of the laser diodes may include one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL).
The photonic integrated circuit may include a plurality of waveguides, each waveguide of the plurality of waveguides to receive laser light from a respective laser diode of the plurality of laser diodes. Each waveguide of the plurality of waveguides may be optimized to receive and output laser light having a wavelength corresponding to the wavelength of laser light received from the respective laser diode. The plurality of waveguides may include a waveguide combiner. The waveguide combiner may include at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Each waveguide of the plurality of waveguides may include an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output couplers of each waveguide being smaller than a spacing between the input facets of each waveguide. Each input facet of the plurality of input facets may be a grating input coupler. Each input facet of the plurality of input facets may be a planar region with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
A method of manufacturing an optical engine may be summarized as including: bonding a plurality of laser diodes directly or indirectly to a base substrate; bonding a cap to the base substrate, the cap comprising at least one wall that, with the base substrate, defines an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap; and bonding a photonic integrated circuit comprising a plurality of input facets and at least one output facet to the cap, in operation, each input facet of the photonic integrated circuit receives a respective beam of light of a plurality of beams of light, and the photonic integrated circuit wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet.
The method may further include: bonding each of the laser diodes indirectly to the base substrate by bonding each laser diode to a respective chip submount; and bonding each chip submount to the base substrate. Bonding each laser diode to a respective chip submount may include bonding each laser diode to a respective chip submount using a eutectic gold tin (AuSn) solder process. Bonding each chip submount to the base substrate may include step-soldering each chip submount to the base substrate. Bonding each chip submount to the base substrate may include bonding each chip submount to the base substrate using at least one of a reflow oven process, thermosonic bonding, thermocompression bonding, transient liquid phase (TLP) bonding, or laser soldering. Bonding each chip submount to the base substrate may include bonding a chip submount that has a red laser diode bonded thereto, bonding a chip submount that has a green laser diode bonded thereto, bonding a chip submount that has a blue laser diode bonded thereto, and bonding a chip submount that has an infrared laser diode bonded thereto.
The method may further include bonding a plurality of collimation lenses between the plurality of laser diodes and the plurality of input facets of the photonic integrated circuit, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward the plurality of input facets of the photonic integrated circuit. Bonding the photonic integrated circuit to the cap may include bonding the plurality of input facets of the photonic integrated circuit against at least one optical window in the cap positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume. Bonding the photonic integrated circuit to the cap may include bonding the photonic integrated circuit to the cap to form at least one optical window in the photonic integrated circuit positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume.
The method may further include providing a coupling between at least one laser diode driver circuit and the plurality of laser diodes, in operation the at least one laser diode driver circuit selectively drives current to the laser diodes. Providing a coupling between at least one laser diode driver circuit and the plurality of laser diodes may include: bonding a plurality of electrical connections to the base substrate, each electrical connection coupled to a respective laser diode in the plurality of laser diodes; providing a coupling between each of the plurality of electrical connections and the at least one laser diode driver circuit; and bonding an electrically insulating cover to the base substrate over the plurality of electrical connections, and bonding the cap to the base substrate may include bonding the cap to the base substrate and the electrically insulating cover. Providing a coupling between each of the plurality of electrical connections and the at least one laser diode driver circuit may include: bonding a plurality of electrical contacts to the base substrate, each electrical contact coupled to a respective one of the plurality of electrical connections; and providing a coupling between each of the electrical contacts and the at least one laser diode driver circuit. Bonding the plurality of laser diodes directly or indirectly to a base substrate may include bonding the laser diodes directly or indirectly to a first surface of the base substrate, and bonding a cap to the base substrate may include bonding a cap to the first surface of the base substrate, and the method may further include bonding the at least one laser diode driver circuit to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. Bonding the plurality of laser diodes directly or indirectly to a base substrate may include bonding the laser diodes directly or indirectly to a first surface of the base substrate, and bonding a cap to the base substrate may include bonding a cap to the first surface of the base substrate, and the method may further include bonding the at least one laser diode driver circuit to the first surface of the base substrate.
Bonding a cap to the base substrate may include bonding a cap to the base substrate using at least one of a seam welding process, a laser assisted soldering process, or a diffusion bonding process. The method may further include prior to bonding the cap to the base substrate, flooding the interior volume with an oxygen rich atmosphere. The method may further include positioning and orienting a collimation lens to receive and collimate the aggregate beam of light from the output coupler of the photonic integrated circuit.
The method may further include laser writing the photonic integrated circuit into writeable glass before bonding the photonic integrated circuit to the cap. Laser writing the photonic integrated circuit into writeable glass may include laser writing a plurality of waveguides into the writeable glass, each waveguide of the plurality of waveguides being written for a respective one laser diode of the plurality of laser diodes. Laser writing a plurality of waveguides into the writeable glass may include writing a waveguide combiner into the writeable glass. Writing a waveguide combiner into the writeable glass may include writing at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Laser writing a plurality of waveguides into the writeable glass may include laser writing each waveguide of the plurality of waveguide to have a input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing of the input facets of each waveguide. Laser writing the photonic integrated circuit into writeable glass may include writing each input facet as a grating input coupler. Laser writing the photonic integrated circuit in writeable glass may include writing each input facet as a planar region with an index of refraction lower than an index of refraction of the writeable glass.
A method of manufacturing an optical engine may be summarized as including: bonding a plurality of laser diodes directly or indirectly to a base substrate; bonding a cap to the base substrate, the cap comprising at least one wall that, with the base substrate, defines an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap; bonding writeable glass to the base substrate; and after bonding the writeable glass to the base substrate, writing a photonic integrated circuit into the writeable glass, the photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at the plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the at least one output facet.
The method may further include: bonding each of the laser diodes indirectly to the base substrate by bonding each laser diode to a respective chip submount; and bonding each chip submount to the base substrate. Bonding each laser diode to a respective chip submount may include bonding each laser diode to a respective chip submount using a eutectic gold tin (AuSn) solder process. Bonding each chip submount to the base substrate may include step-soldering each chip submount to the base substrate. Bonding each chip submount to the base substrate may include bonding each chip submount to the base substrate using at least one of a reflow oven process, thermosonic bonding, thermocompression bonding, transient liquid phase (TLP) bonding, or laser soldering. Bonding each chip submount to the base substrate may include bonding a chip submount that has a red laser diode bonded thereto, bonding a chip submount that has a green laser diode bonded thereto, bonding a chip submount that has a blue laser diode bonded thereto, and bonding a chip submount that has an infrared laser diode bonded thereto.
The method may further include bonding a plurality of collimation lenses between the plurality of laser diodes and the plurality of input facets of the photonic integrated circuit, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward the plurality of input facets of the photonic integrated circuit. Bonding the writeable glass to the cap may include bonding the writable glass against at least one optical window in the cap positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume. Bonding the writeable glass to the cap may include bonding the writeable glass to the cap to form at least one optical window in the writable glass positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume.
The method may further include providing a coupling between at least one laser diode driver circuit and the plurality of laser diodes, in operation the at least one laser diode driver circuit selectively drives current to the laser diodes. Providing a coupling between at least one laser diode driver circuit and the plurality of laser diodes may include: bonding a plurality of electrical connections to the base substrate, each electrical connection coupled to a respective laser diode in the plurality of laser diodes; providing a coupling between each of the plurality of electrical connections and the at least one laser diode driver circuit; and bonding an electrically insulating cover to the base substrate over the plurality of electrical connections, and bonding the cap to the base substrate may include bonding the cap to the base substrate and the electrically insulating cover. Providing a coupling between each of the plurality of electrical connections and the at least one laser diode driver circuit may include: bonding a plurality of electrical contacts to the base substrate, each electrical contact coupled to a respective one of the plurality of electrical connections; and providing a coupling between each of the electrical contacts and the at least one laser diode driver circuit.
Bonding the plurality of laser diodes directly or indirectly to a base substrate may include bonding the laser diodes directly or indirectly to a first surface of the base substrate, and bonding a cap to the base substrate may include bonding a cap to the first surface of the base substrate, the method may further include bonding the at least one laser diode driver circuit to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate. Bonding the plurality of laser diodes directly or indirectly to a base substrate may include bonding the laser diodes directly or indirectly to a first surface of the base substrate, and bonding a cap to the base substrate may include bonding a cap to the first surface of the base substrate, the method may further include bonding the at least one laser diode driver circuit to the first surface of the base substrate.
Bonding a cap to the base substrate may include bonding a cap to the base substrate using at least one of a seam welding process, a laser assisted soldering process, or a diffusion bonding process. The method may further include prior to bonding the cap to the base substrate, flooding the interior volume with an oxygen rich atmosphere. The method may further include positioning and orienting a collimation lens to receive and collimate the aggregate beam of light from the at least one output facet of the photonic integrated circuit.
Laser writing the photonic integrated circuit into the writeable glass may include laser writing a plurality of waveguides into the writeable glass, each waveguide of the plurality of waveguides being written for a respective one laser diode of the plurality of laser diodes. Laser writing a plurality of waveguides into the writeable glass may include writing a waveguide combiner into the writeable glass. Writing a waveguide combiner into the writeable glass may include writing at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler. Laser writing a plurality of waveguides into the writeable glass may include laser writing each waveguide of the plurality of waveguides to have an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing of the input facets of each waveguide.
Laser writing the photonic integrated circuit into the writeable glass may include writing each input facet as a grating input coupler. Laser writing the photonic integrated circuit in the writeable glass may include writing each input facet as a planar region with an index of refraction lower than an index of refraction of the writeable glass.
In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not necessarily intended to convey any information regarding the actual shape of the particular elements, and may have been solely selected for ease of recognition in the drawings.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations. However, one skilled in the relevant art will recognize that implementations may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with computer systems, server computers, and/or communications networks have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations.
Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprising” is synonymous with “including,” and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or method acts).
Reference throughout this specification to “one implementation” or “an implementation” means that a particular feature, structure or characteristic described in connection with the implementation is included in at least one implementation. Thus, the appearances of the phrases “in one implementation” or “in an implementation” in various places throughout this specification are not necessarily all referring to the same implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the context clearly dictates otherwise.
The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations.
One or more implementations of the present disclosure provide laser-based optical engines, for example, laser-based optical engines for laser projectors used in wearable heads-up displays or other applications. Generally, the optical engines discussed herein integrate a plurality of laser dies or diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. As discussed further below with reference to
The optical engine 100 also includes a plurality of chip submounts 108a-108d (collectively 108) bonded (e.g., attached) to the top surface 104 of the base substrate 102. The plurality of chip submounts 108 are aligned in a row across a width of the optical engine 100 between the left and right sides thereof. Each of the plurality of chip submounts 108 includes a laser diode 110, also referred to as a laser chip or laser die, bonded thereto. In particular, an infrared chip submount 108a carries an infrared laser diode 110a, a red chip submount 108b carries a red laser diode 110b, a green chip submount 108c carries a green laser diode 110c, and a blue chip submount 108d carries a blue laser diode 110d. In operation, the infrared laser diode 110a provides infrared laser light, the red laser diode 110b provides red laser light, the green laser diode 110c provides green laser light, and the blue laser diode 110d provides blue laser light. Each of the laser diodes 110 may comprise one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL), for example. Each of the four laser diode/chip submount pairs may be referred to collectively as a “laser chip on submount,” or a laser CoS 112. Thus, the optical engine 100 includes an infrared laser CoS 112a, a red laser CoS 112b, a green laser CoS 112c, and a blue laser CoS 112d. In at least some implementations, one or more of the laser diodes 110 may be bonded directly to the base substrate 102 without use of a submount 108. It should be appreciated that although some implementations discussed herein describe laser diodes as chips or dies on submounts, other dies or types of devices, e.g., p-side down devices, may be used as well.
The optical engine 100 also includes a laser diode driver circuit 114 bonded to the bottom surface 106 of the base substrate 102. The laser diode driver circuit 114 is operatively coupled to the plurality of laser diodes 110 via suitable electrical connections 116 to selectively drive current to the plurality of laser diodes. In at least some implementations, the laser diode driver circuit 114 may be positioned relative to the CoSs 112 to minimize the distance between the laser diode driver circuit 114 and the CoSs 112. Although not shown in
Proximate the laser diodes 110 there is positioned an optical director element 118. Like the chip submounts 108, the optical director element 118 is bonded to the top surface 104 of the base substrate 102. In the illustrated example, the optical director element 118 has a triangular prism shape that includes a plurality of planar faces. In particular the optical director element 118 includes an angled front face 118a that extends along the width of the optical engine 100, a rear face 118b, a bottom face 118c that is bonded to the top surface 104 of the base substrate 102, a left face 118d, and a right face 118e opposite the left face. The optical director element 118 may comprise a mirror or a prism, for example.
The optical engine 100 also includes a cap 120 that includes a vertical sidewall 122 having a lower first end 124 and an upper second end 126 opposite the first end. A flange 128 may be disposed around a perimeter of the sidewall 122 adjacent the lower first end 124. Proximate the upper second end 126 of the sidewall 122 there is a horizontal optical window 130 that forms the “top” of the cap 120. The sidewall 122 and the optical window 130 together define an interior volume 132 sized and dimensioned to receive the plurality of chip submounts 108, the plurality of laser diodes 110, and the optical director element 118. The lower first end 124 and the flange 128 of the cap 120 are bonded to the base substrate 102 to provide a hermetic or partially hermetic seal between the interior volume 132 of the cap and a volume 134 exterior to the cap.
As shown best in
The cap 120 may have a round shape, rectangular shape, or other shape. Thus, the vertical sidewall 122 may comprise a continuously curved sidewall, a plurality (e.g., four) of adjacent planar portions, etc. The optical window 130 may comprise an entire top of the cap 120, or may comprise only a portion thereof. In at least some implementations, the optical window 130 may be located on the sidewall 122 rather than positioned as a top of the cap 120, and the laser diodes 110 and/or the optical director element 118 may be positioned and oriented to direct the laser light from the laser diodes toward the optical window on the sidewall 122. At least some implementations may not include optical director element 118 such that laser light from the laser diodes may be output towards the optical window on the sidewall 122 without the need for intervening optical elements. In at least some implementations, the cap 120 may include a plurality of optical windows instead of a single optical window.
The optical engine 100 also includes four collimation/pointing lenses 136a-136d (collectively 136), one for each of the four laser diodes 110a-110d, respectively, that are bonded to a top surface 138 of the optical window 130. Each of the plurality of collimation lenses 136 is positioned and oriented to receive light from a corresponding one of the laser diodes 110 through the optical window 130. In particular, the collimation lens 136a receives light from the infrared laser diode 110a via the optical director element 118 and the optical window 130, the collimation lens 136b receives light from the red laser diode 110b via the optical director element and the optical window, the collimation lens 136c receives light from the green laser diode 110c via the optical director element and the optical window, and the collimation lens 136d receives light from the blue laser diode 110d via the optical director element and the optical window.
Each of the collimation lenses 136 is operative to receive laser light from a respective one of the laser diodes 110, and to generate a single color beam. In particular, the collimation lens 136a receives infrared laser light from the infrared laser diode 110a and produces an infrared laser beam 138a, the collimation lens 136b receives red laser light from the red laser diode 110b and produces a red laser beam 138b, the collimation lens 136c receives green laser light from the green laser diode 110c and produces a green laser beam 138c, and the collimation lens 136d receives blue laser light from the blue laser diode 110d and produces a blue laser beam 138d.
The optical engine 100 may also include, or may be positioned proximate to, a beam combiner 140 that is positioned and oriented to combine the light beams 138a-138d received from each of the collimation lenses 136 into a single aggregate beam 142. As an example, the beam combiner 140 may include one or more diffractive optical elements (DOE) and/or refractive/reflective optical elements that combine the different color beams 138a-138d in order to achieve coaxial superposition. An example beam combiner is shown in
In at least some implementations, the laser CoSs 112, the optical director element 118, and/or the collimation lenses 136 may be positioned differently. As noted above, laser diode driver circuit 114 may be mounted on the top surface 104 or the bottom surface 106 of the base substrate 102, depending on the RF design and other constraints (e.g., package size). In at least some implementations, the optical engine 100 may not include the optical director element 118, and the laser light may be directed from the laser diodes 110 toward the collimation lenses 136 without requiring an intermediate optical director element. Additionally, in at least some implementations, one or more of the laser diodes may be mounted directly on the base substrate 102 without use of a submount. For the sake of a controlled atmosphere inside the interior volume 132, it may be desirable to have no organic compounds inside the interior volume 132. In at least some implementations, the components of the optical engine 100 may be bonded together using no adhesives. In other implementations, a low amount of adhesives may be used to bond at least one of the components, which may reduce cost while providing a relatively low risk of organic contamination for a determined lifetime (e.g., 2 or more years) of the optical engine 100. The use of adhesives may result in a partial hermetic seal, but this partial hermetic seal may be acceptable in certain applications, as detailed below.
Generally, “hermetic” refers to a seal which is airtight, that is, a seal which excludes the passage of air, oxygen, and other gases. “Hermetic” within the present specification carries this meaning. Further, “partially hermetic” as used herein refers to a seal which limits, but does not necessarily completely prevent, the passage of gases such as air. “Partially hermetic” as used herein may alternatively be stated as “reduced hermiticity”. In the example above, adhesives may be used to bond components. Such adhesives may result in a seal being not completely hermetic, in that some amount of gasses may slowly leak through the adhesive. However, such a seal can still be considered “partially hermetic” or as having “reduced hermiticity”, because the seal reduces the flow of gasses therethrough.
In one example application, even in an environment with only partial hermiticity, the life of laser diodes 110 and transparency of optical window 130 may be maintained longer than the life of a battery of a device, such that partial hermiticity may be acceptable for the devices. In some cases, even protecting interior volume 132 from particulate with a dust cover may be sufficient to maintain laser diodes 110 and transparency of optical window 130 for the intended lifespan of the device. In some cases, laser diodes 110 and transparency of optical window 130 may last for the intended lifespan of the device even without a protective cover. Various bonding processes (e.g., attaching processes) for the optical engine 100 are discussed below with reference to
At 202, at least one controller may cause a plurality of laser diodes of an optical engine to generate laser light. As discussed above, the plurality of laser diodes may be hermetically or partially hermetically sealed in an encapsulated package. The laser diodes may produce light sequentially and/or simultaneously with each other. At 204, at least one optical director element may optionally receive the laser light from the laser diodes. The optical director element may comprise a mirror or a prism, for example. As discussed above, in at least some implementations the optical engine may be designed such that laser light exits the optical engine without use of an optical director element.
At 206, the at least one optical director element, if included, may direct the received laser light toward an optical window of the encapsulated package. For example, the optical director element may reflect the received laser light toward the optical window of the encapsulated package. In implementations without at least one optical director element, the laser light generated by the plurality of laser diodes may be output directly toward the optical window of the encapsulated package.
At 208, a plurality of collimation lenses may collimate the laser light from the laser diodes that exits the encapsulated package via the optical window to generate a plurality of differently colored laser light beams. The collimation lenses may be positioned inside or outside of the encapsulated package. As an example, the collimation lenses may be physically coupled to the optical window of the encapsulated package.
At 210, a beam combiner may combine the plurality of laser light beams received from each of the collimation lenses into a single aggregate beam. The beam combiner may include one or more diffractive optical elements (DOE) that combine different color beams in order to achieve coaxial superposition, for example. The beam combiner may include one or more DOEs and/or one or more refractive/reflective optical elements. An example beam combiner is shown in
The laser projector 302 comprises a controller or processor 310, an optical engine 312 comprising four laser diodes 314a, 314b, 314c, 314d (collectively 314) communicatively coupled to the processor 310, a beam combiner 316, and a scan mirror 318. The optical engine 312 may be similar or identical to the optical engine 100 discussed above with reference to
During operation of the WHUD 300, the processor 310 modulates light output from the laser diodes 314, which includes a first red laser diode 314a (R), a second green laser diode 314b (G), a third blue laser diode 314c (B), and a fourth infrared laser diode 314d (IR). The first laser diode 314a emits a first (e.g., red) light signal 320, the second laser diode 314b emits a second (e.g., green) light signal 322, the third laser diode 314c emits a third (e.g., blue) light signal 324, and the fourth laser diode 314d emits a fourth (e.g., infrared) light signal 326. All four of light signals 320, 322, 324, and 326 enter or impinge on the beam combiner 316. Beam combiner 316 could for example be based on any of the beam combiners described in U.S. Provisional Patent Application Ser. No. 62/438,725, U.S. Non-Provisional patent application Ser. No. 15/848,265 (U.S. Publication Number 2018/0180885), U.S. Non-Provisional patent application Ser. No. 15/848,388 (U.S. Publication Number 2018/0180886), U.S. Provisional Patent Application Ser. No. 62/450,218, U.S. Non-Provisional patent application Ser. No. 15/852,188 (U.S. Publication Number 2018/0210215), U.S. Non-Provisional patent application Ser. No. 15/852,282, (U.S. Publication Number 2018/0210213), and/or U.S. Non-Provisional patent application Ser. No. 15/852,205 (U.S. Publication Number 2018/0210216).
In the illustrated example, the beam combiner 316 includes optical elements 328, 330, 332, and 334. The first light signal 320 is emitted towards the first optical element 328 and reflected by the first optical element 328 of the beam combiner 316 towards the second optical element 330 of the beam combiner 316. The second light signal 322 is also directed towards the second optical element 330. The second optical element 330 is formed of a dichroic material that is transmissive of the red wavelength of the first light signal 320 and reflective of the green wavelength of the second light signal 322. Therefore, the second optical element 330 transmits the first light signal 320 and reflects the second light signal 322. The second optical element 330 combines the first light signal 320 and the second light signal 322 into a single aggregate beam (shown as separate beams for illustrative purposes) and routes the aggregate beam towards the third optical element 332 of the beam combiner 316.
The third light signal 324 is also routed towards the third optical element 332. The third optical element 332 is formed of a dichroic material that is transmissive of the wavelengths of light (e.g., red and green) in the aggregate beam comprising the first light signal 320 and the second light signal 322 and reflective of the blue wavelength of the third light signal 324. Accordingly, the third optical element 332 transmits the aggregate beam comprising the first light signal 320 and the second light signal 322 and reflects the third light signal 324. In this way, the third optical element 332 adds the third light signal 324 to the aggregate beam such that the aggregate beam comprises the light signals 320, 322, and 324 (shown as separate beams for illustrative purposes) and routes the aggregate beam towards the fourth optical element 334 in the beam combiner 316.
The fourth light signal 326 is also routed towards the fourth optical element 334. The fourth optical element 334 is formed of a dichroic material that is transmissive of the visible wavelengths of light (e.g., red, green, and blue) in the aggregate beam comprising the first light signal 320, the second light signal 322, and the third light signal 324 and reflective of the infrared wavelength of the fourth light signal 326. Accordingly, the fourth optical element 334 transmits the aggregate beam comprising the first light signal 320, the second light signal 322, and the third light signal 324 and reflects the fourth light signal 326. In this way, the fourth optical element 334 adds the fourth light signal 326 to the aggregate beam such that the aggregate beam 336 comprises portions of the light signals 320, 322, 324, and 326. The fourth optical element 334 routes the aggregate beam 336 towards the controllable scan mirror 318.
The scan mirror 318 is controllably orientable and scans (e.g. raster scans) the beam 336 to the eye 306 of the user of the WHUD 300. In particular, the controllable scan mirror 318 scans the laser light onto the transparent combiner 304 carried by the eyeglass lens 308. The scan mirror 318 may be a single bi-axial scan mirror or two single-axis scan mirrors may be used to scan the laser light onto the transparent combiner 304, for example. In at least some implementations, the transparent combiner 304 may be a holographic combiner with at least one holographic optical element. The transparent combiner 304 redirects the laser light towards a field of view of the eye 306 of the user. The laser light redirected towards the eye 306 of the user may be collimated by the transparent combiner 304, wherein the spot at the transparent combiner 304 is approximately the same size and shape as the spot at the eye 306 of the user. The laser light may be converged by the eye 306 to a focal point at the retina of eye 306 and creates an image that is focused. The visible light may create display content in the field of view of the user, and the infrared light may illuminate the eye 306 of the user for the purpose of eye tracking.
In operation of the WHUD 400, the controller 410 controls the laser projector 402 to emit laser light. As discussed above with reference to
At 502, a plurality of laser diodes may be bonded to a respective plurality of submounts. In at least some implementations, this method may be performed by an entity different than that manufacturing the optical engine. For example, in at least some implementations, one or more of the plurality of laser diodes (e.g., green laser diode, blue laser diode) may be purchased as already assembled laser CoSs. For ease of handling and simplification of the overall process, in at least some implementations it may be advantageous to also bond laser diodes that cannot be procured on submounts to a submount as well. As a non-limiting example, in at least some implementations, one or more of the laser diodes may be bonded to a corresponding submount using an eutectic gold tin (AuSn) solder process, which is flux-free and requires heating up top 280° C.
At 504, the plurality of CoSs may be bonded to a base substrate. Alternatively, act 502 could be skipped for at least one or all of the laser diodes, and act 504 could comprise bonding the at least one or all of the laser diodes directly to the base substrate. The base substrate may be formed from a material that is RF compatible and is suitable for hermetic sealing. For example, the base substrate may be formed from low temperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc. Since several CoSs are bonded next to each other on the same base substrate, it may be advantageous to either “step-solder” them sequentially or to use a bonding technique that does not rely on re-melting of solder materials. For step-soldering, each subsequent soldering step utilizes a process temperature that is less than the process temperatures of previous solder steps to prevent re-melting of solder materials. It may also be important that the laser diode-to-submount bonding does not re-melt during bonding of the CoSs to the base substrate. Bonding technologies other than step-soldering that may be used include parallel soldering of all CoS in reflow oven process, thermosonic or thermocompression bonding, transient liquid phase (TLP) bonding, laser soldering, etc. Some of these example bonding technologies are discussed below.
For parallel soldering of all CoSs in a reflow oven process, appropriate tooling is required to assure proper bonding and alignment during the process. An advantage of this process is the parallel and hence time efficient bonding of all CoSs at once and even many assemblies in parallel. A possible disadvantage of this process is the potential loss of the alignment of components during the reflow process. Generally, a soldering cycle ideally needs a few minutes of dwell time. Preheating may be used to reduce the soldering time, which requires a few minutes for such a process depending on the thermal mass of the components being bonded. Thus, a batch process may be used with regular soldering to reduce the assembly costs with high throughput at the expense of alignment tolerance.
For thermosonic or thermocompression bonding, thick gold metallization may be used but no extra solder layer is required. The temperatures for thermocompression bonding might be as high as 300 to 350° C. to have a good bond with a good thermal conductivity. Thermosonic bonding may be used to reduce the pressure and temperature needed for bonding, which may be required for at least some components that might not tolerate the temperatures required for thermocompression bonding.
Transient liquid phase (TLP) bonding may also be used. There are many different reaction couples that may be used, including gold-tin, copper-tin, etc. With this method, a liquid phase is formed during the bonding which will solidify at the same temperature. The re-melting temperatures of the bond are much higher than the soldering temperatures.
In at least some implementations, laser soldering may be used to bond some or all of the components of the optical engine. Generally, the thermal characteristic of the parts to be bonded may be important when implementing a laser soldering process.
Subsequent reflows of solder are not recommended due to liquid phase reaction or dissolution mechanisms which may reduce the reliability of the joint. This could result in voiding at the interface or a reduction in strength of the joint itself. In order to mitigate potential reflow dissolution problems, other options can be taken into consideration, which do not rely on extreme heating of the device and can be favorable in terms of production cost. For example, bonding of the base substrate with adhesives (electrically conductive for common mass, or non-conductive for floating) may be acceptable with respect to heat transfer and out-gassing as discussed regarding partial hermetic sealing above.
Further, in at least some implementations, a reactive multi-layer foil material (e.g., NanoFoil®) or a similar material may be used as a solder pre-form, which enables localized heat transfer. A reactive multi-layer foil material is a metallic material based on a plurality (e.g., hundreds, thousands) of reactive foils (aluminum and nickel) that enables die-attach soldering (e.g., silicon chip onto stainless steel part). In such implementations, dedicated heat transfer support metallizations may be deposited onto the two components being joined together. This method may be more advantageous for CoS-to-base substrate mounting compared to chip-to-submount bonding. Generally, bonding using reactive multi-layer foil materials enables furnace-free, low-temperature soldering of transparent or non-transparent components, without reaching the bonding temperatures for solder reflow processes. Reactive multi-layer foil materials can be patterned with a ps-laser into exact preform shapes.
At 506, the optical director element, if included, may be bonded to the base substrate proximate the laser CoSs. The optical director element may be bonded to the base substrate using any suitable bonding process, including the bonding processes discussed above with reference to act 504.
At 508, the laser diode driver circuit may optionally be bonded to the base substrate. As noted above, the laser diode driver circuit may be bonded to the base substrate such that the distance between the laser diode driver circuit and the laser CoSs is minimized. This may also comprise positioning a plurality of electrical connections which operatively couple the laser diode driver circuit to the plurality of laser diodes as shown in
At 510, the cap may be bonded to the base substrate to form a hermetic or partially hermetic seal between the interior volume of the encapsulated package and an exterior environment. As noted above, it may be desirable to maintain a specific atmosphere for the laser diode chips for reliability reasons. In at least some implementations, adhesive sealing may be undesirable because of the high permeability of gases. This is especially the case for blue laser diodes, which emit blue laser light that may bake contamination on facets and windows, thereby reducing transparency of the optical window. However, as detailed above regarding
During the sealing process, the atmosphere may be defined by flooding the package accordingly. For example, the interior volume of the encapsulated package may be flooded with an oxygen enriched atmosphere that burns off contaminants which tend to form on interfaces where the laser beam is present. The sealing itself may also be performed so as to prevent the exchange between the package atmosphere and the environment. Due to limitations concerning the allowed sealing temperature, e.g., the components inside the package should not be influenced, in at least some implementations seam welding or laser assisted soldering/diffusion bonding may be used. In at least some implementations, localized sealing using a combination of seam welding and laser soldering may be used.
At 512, the collimation lenses may be actively aligned. For example, once the laser diode driver circuit has been bonded and the cap has been sealed, the laser diodes can be turned on and the collimations lenses for each laser diode can be actively aligned. In at least some implementations, each of the collimation lenses may be positioned to optimize spot as well as pointing for each of the respective laser diodes.
At 514, the beam combiner may be positioned to receive and combine individual laser beams into an aggregate beam. As discussed above, the beam combiner may include one or more diffractive optical elements and/or one or more refractive/reflective optical elements that function to combine the different color beams into an aggregate beam. The aggregate beam may be provided to other components or modules, such as a scan mirror of a laser projector, etc.
Following out-coupling of the aggregate beam 614 from the output facet 608 of the photonic integrated circuit 600, the aggregated beam is collimated via the common collimation lens 602. In at least some implementations, the collimation lens 602 may be either an achromatic lens or an apochromatic lens (or lens assemblies), depending on the particular optical design and tolerances of the system. In at least some implementations, one or more diffractive optical elements 604 may be used to provide wavelength dependent focus correction.
The optical engine 700 includes a base substrate 702 having a top surface 704 and a bottom surface 706 opposite the top surface. The base substrate 702 may be formed from a material that is radio frequency (RF) compatible and is suitable for hermetic sealing. For example, the base substrate 702 may be formed from low temperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.
The optical engine 700 also includes a plurality of chip submounts 708 (only one chip submount visible in the sectional view of
The optical engine 700 also includes a laser diode driver circuit 714 bonded to the bottom surface 706 of the base substrate 702. The laser diode driver circuit 714 is operatively coupled to the plurality of laser diodes 710 via suitable electrical connections 716 to selectively drive current to the plurality of laser diodes. Generally, the laser diode driver circuit 714 may be positioned relative to the CoSs 712 to minimize the distance between the laser diode driver circuit 714 and the CoSs 712. Although not shown in
Proximate the laser diodes 710 there is positioned an optical director element 718. Like the chip submounts 708, the optical director element 718 is bonded to the top surface 704 of the base substrate 702. In the illustrated example, the optical director element 718 has a triangular prism shape that includes a plurality of planar faces. In particular the optical director element 718 includes an angled front face 718a that extends along the width of the optical engine 700, a rear face 718b, a bottom face 718c that is bonded to the top surface 704 of the base substrate 702, a left face 718d, and a right face 718e opposite the left face. The optical director element 718 may comprise a mirror or a prism, for example. In at least some implementations, the angled front face 718a may be curved to provide fast axis collimation of the laser light from the laser diodes 710.
The optical engine 700 also includes a cap 720 that includes a vertical sidewall 722 having a lower first end 724 and an upper second end 726 opposite the first end. A flange 728 may be disposed around a perimeter of the sidewall 722 adjacent the lower first end 724. Proximate the upper second end 726 there of the sidewall 722 there is a horizontal (as shown) optical window 730 that forms the “top” of the cap 120. The sidewall 722 and the optical window 730, along with a portion of the top surface 704 of the base substrate 702, together define an interior volume 732 sized and dimensioned to receive the plurality of chip submounts 708, the plurality of laser diodes 710, and the optical director element 717. The lower first end 724 and the flange 728 of the cap 720 are bonded to the base substrate 702 to provide a hermetic or partially hermetic seal between the interior volume 732 of the cap and a volume 734 exterior to the cap.
The optical director element 718 is positioned and oriented to direct (e.g., reflect) laser light received from each of the plurality of laser diodes 710 upward (as shown) toward the optical window 730 of the cap 720, wherein the laser light exits the interior volume 732.
The cap 720 may have a round shape, rectangular shape, or other shape. Thus, the vertical sidewall 722 may comprise a continuously curved sidewall, a plurality (e.g., four) of adjacent planar portions, etc. The optical window 730 may comprise an entire top of the cap 720, or may comprise only a portion thereof. In at least some implementations, the optical window 730 may be located on the sidewall 722 rather than positioned as a top of the cap 720, and the laser diodes 710 and/or the optical director element 718 (if present) may be positioned and oriented to direct the laser light from the laser diodes toward the optical window on the sidewall 722. In at least some implementations, the cap 720 may include a plurality of optical windows instead of a single optical window 730.
In at least some implementations, the optical engine 700 optionally includes four collimation lenses 736 (only one visible in the sectional view of
The optical director element 718 and the collimation lenses 736 (when present) direct the beams of light 610a-610d (see
In at least some implementations, the laser diodes 710 may be directly coupled to the photonic integrated circuit 600. In such implementations, the laser diodes 710 may be positioned immediately adjacent to a waveguide structure (e.g., photonic integrated circuit or other waveguide structure) such that sufficient coupling (e.g., acceptable insertion loss) is achieved. For example, in at least some implementations, the photonic integrated circuit 600 may function as the optical window of the package itself. Following out-coupling of the aggregate beam 614 from the output facet 608 of the photonic integrated circuit 600, the aggregated beam may be collimated via the common collimation lens 602. In at least some implementations, the common collimation lens 602 may be bonded to the top surface 704 proximate the photonic integrated circuit 600. In at least some implementations, the collimation lens 602 may be either an achromatic lens or an apochromatic lens, depending on the particular optical design and tolerances of the system. In at least some implementations, the optical engine 700 may include one or more diffractive optical elements 604 to provide wavelength dependent focus correction.
In at least some implementations, at least some of the components may be positioned differently. As noted above, the laser diode driver circuit 714 may be mounted on the top surface 704 or the bottom surface 706 of the base substrate 702, or may be positioned remotely therefrom, depending on the RF design and other constraints (e.g., package size), similarly to as discussed with reference to
For the sake of a controlled atmosphere inside the interior volume 732, it may be desirable to have no organic compounds inside the interior volume 732. In at least some implementations, the components of the optical engine 700 may be bonded together using no adhesives. In other implementations, a low amount of adhesives may be used to bond at least one of the components, which may reduce cost while providing a relatively low risk of organic contamination for a determined lifetime (e.g., 2 or more years) of the optical engine 700. Similarly to as detailed above regarding
In at least some implementations, the collimation lenses 736 (when present) and the collimation lens 602 may be actively aligned. In at least some implementations, the CoSs 712, the cap 720 (including optical window 730), and/or the photonic integrated circuit 600 may be passively aligned. Further, depending on the particular design, it may be advantageous to utilize a smaller base substrate 702 and use an additional carrier substrate instead.
Writeable glass 820 can be physically coupled to translatable mount 830, such as by using clamps 821, adhesive, or any other appropriate coupling mechanism. Such coupling mechanism is preferably removable, such that writeable glass 820 can be detached from translatable mount 830 after laser writing is complete. Translation of translatable mount 830 in the X, Y, and/or Z direction will result in corresponding translation of writeable glass 820, moving the location of focal point 813 within writeable glass 820. Translating the writeable glass 820 relative to focal point 813 can create a region of changed refractive index in the writeable glass 820. An increased refractive index in this region causes any light channeled therethrough to experience total internal reflection, thus forming waveguide 822. In other words, waveguide 822 can be formed as a continuous path of increased refractive index within writeable glass 820 created by laser light 811 at focal point 813.
The technique of
Writing at least one waveguide may include writing an individual waveguide for each wavelength of light impinging on the writeable glass 820, where each waveguide comprises a respective input facet (such as an input grating coupler) and a respective output facet. Each output facet may be positioned to provide light to other components or modules, such as a scan mirror of a laser projector, etc. In one implementation, four waveguides could be written into writeable glass 820, one waveguide for each beam of light 610a, 610b, 610c, and 610d. Four grating couplers could also be written, one for each waveguide.
Writing at least one waveguide may include writing a waveguide combiner, wherein the waveguide combiner combines individual laser beams into a coaxially superimposed aggregate beam. Writing a waveguide combiner may include writing at least one: directional coupler (DC), Y-branch, whispering gallery mode coupler, or multi-mode interference coupler. The aggregate beam may be provided to other components or modules, such as a scan mirror of a laser projector, etc.
In other implementations, the photonic integrated circuit 600 may include one or more diffractive optical elements (DOE) and/or refractive/reflective optical elements that combine the different color beams 610a-d in order to achieve coaxial superposition.
Alternatively, instead of writing a waveguide combiner, individual waveguides could be written which do not strictly coaxially superimpose the beams of light, but instead bring each beam of light close together. That is, the input facet (e.g. grating coupler) for each waveguide in the photonic integrated circuit can be positioned relatively far from the other input facets, to receive laser light from a respective laser diode, but the output facets for each of the waveguides can be positioned relatively close together. In other words, a spacing between the output facets of each waveguide can be smaller than a spacing of the input facets of each waveguide. In such an implementation, each waveguide can be optimized for performance with light of a corresponding wavelength, for example to ensure that each wavelength of light exits the photonic integrated circuit with the same divergence angle as each other wavelength. The output of each individual waveguide can be placed close enough together (on the order of 10s of microns) such that that the light output by each individual waveguide may still follow the same optical path through the rest of a projector, display, or WHUD assembly where the photonic integrated circuit is implemented.
Method 900 can include at least acts 902, 904, 906, 908, 910, 912, 914, and 916. Acts 902, 904, 906, 908, and 910 substantially correspond to acts 502, 504, 506, 508, and 510, respectively, of method 500 in
At 912, a photonic integrated circuit is laser written in writeable glass, using for example the techniques described with regards to
At 914, the writeable glass including the photonic integrated circuit is bonded to the cap. Any appropriate bonding technique may be used, including those described with reference to acts 502, 504, 506, 508, and 510 in
In order for light to travel through a photonic integrated circuit, the light emitted by each laser diode should preferably be aligned with a respective input facet of the photonic integrated circuit with high precision; mis-alignment of greater than 10 micrometers may significantly reduce the efficiency of the photonic integrated circuit. An output facet of each laser diode may have dimensions smaller than four square micrometers; aligning such small components to such high precision presents a non-trivial technical challenge.
In one implementation, each input facet of the photonic integrate circuit could be written as a grating coupler as shown in
In act 916, a collimation lens may be provided such that a coaxially superimposed beam of light from the output edge of the photonic integrated circuit will be collimated by the collimation lens. The collimation lens may optionally optimize the spot (e.g., circularize) the coaxially superimposed beam. In some implementations, more than one collimation lens may be provided if the light output from the photonic integrated circuit is not a fully coaxially superimposed beam. The collimation lens or lenses may be actively aligned after the other components are assembled, or may be passively aligned such that appropriate alignment is achieved during assembly.
As mentioned above, aligning a photonic integrated circuit such that each input facet of the photonic integrated circuit lines up with a beam of light emitted by each laser diode with high-precision presents a non-trivial challenge. The present systems, devices, and methods provide a solution to this challenge, by producing photonic integrated circuits where the fabrication process includes an alignment process, obviating the need for a later mechanical alignment process, as discussed below with reference to
Writeable glass 820 is bonded to cap 720 prior to writing a photonic integrated circuit therein, using any of the bonding techniques discussed above. The writeable glass 820 may comprise a contiguous piece of glass or similar transparent material that undergoes a change in refractive index when exposed to high-intensity laser light. Bonding the writeable glass to the cap includes positioning and orienting the writeable glass 820 relative to each laser diode 710 to place the writeable glass 820 in the path of the beam of light emitted by each laser diode 710, such that the beam of light emitted by each laser diode 710 impinges on the writeable glass.
Writeable glass 820 can be positioned against optical window 730, such that beams of light from laser diodes 710 pass through optical window 730 directly into writeable glass 820. Alternatively, the writeable glass 820 may optionally form optical window 730.
The entire base substrate 702 and all components bonded thereto can be physically coupled to translatable mount 830, such as with clamps 821, adhesives, and/or any other appropriate coupling mechanism. Such coupling mechanism is preferably removable, such that base substrate 702 and all components bonded thereto can be detached from translatable mount 830 after laser writing of writeable glass 820 is complete.
With writeable glass 820 bonded to base substrate 702 indirectly via cap 720, and base substrate 702 physically coupled to translatable mount 830, at least one waveguide 822 can be laser written into writeable glass 820 by translating base substrate 702 and all components thereon using translatable mount 830. At least one input facet 612 (for example at least one grating input coupler) can also be written into writeable glass 820 by translating base substrate 702 and all components thereon using translatable mount 830. Consequently, writeable glass 820 becomes a photonic integrated circuit.
To determine where the at least one waveguide 822 should be written, laser diodes 710 could be activated, thus causing beams of light therefrom to impinge on writeable glass 820. Writing laser 810 can be aligned to directly write waveguides and input facets (e.g. grating couplers as shown in
Alternatively, the writeable glass 820 could be illuminated, such as by being backlit if base substrate 702 is at least partially transparent. Writing laser 810 can then be aligned to directly write waveguides based on locations of shadows caused by laser diodes 710, CoS's 712 and optical redirector element 718. In this way, the input facets of the resulting photonic integrated circuit will be accurately aligned with the laser diodes, ensuring efficient incoupling of the beams of light into the photonic integrated circuit. Aligning the input facets of the photonic integrated circuit to the beams of light during the writing stage will be more accurate than trying to mechanically align a pre-fabricated photonic integrated circuit, due to deviations that can arise in the bonding processes of not only the pre-fabricated photonic integrate circuit, but also the laser diodes. As one example, if each of four laser diodes is randomly misaligned, it would be difficult to align a prefabricated photonic integrated circuit to match the beam of light from each diode, since not only could the photonic integrated circuit be misaligned during the bonding processes, but also the spacing between each laser diode may not match the spacing between each waveguide in the photonic integrated circuit due to the random misalignment of each of the laser diodes. Direct laser writing the photonic integrated circuit after all of the components have been mechanically bonded obviates these issues, by allowing the position and spacing of each laser diode relative to the writeable glass to be accounted for after bonding is complete.
In
Additionally,
In some implementations, a photonic integrated circuit could be manufactured using a combination of the techniques described with reference to
In one example, a large portion of a photonic integrated circuit could be first written, except for a small portion of the photonic integrated circuit at the input of writeable glass. Subsequently, the photonic integrated circuit could be bonded to the cap such as in
In another example, a first photonic integrated circuit could be written as in
The optical engine 1100a also includes a plurality of laser diodes aligned in a row across a width of the optical engine 1100a, including an infrared laser diode 1110a, a red laser diode 1110b, a green laser diode 1110c, and a blue laser diode 1110d. In operation, the infrared laser diode 1110a provides infrared laser light, the red laser diode 1110b provides red laser light, the green laser diode 1110c provides green laser light, and the blue laser diode 1110d provides blue laser light. Each of the laser diodes may comprise one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL), for example. In
The optical engine 1100a also includes a laser diode driver circuit 1114 which can be bonded to the same surface of base substrate 1102 as the laser diodes 1110a, 1110b, 1110c, 1110d. In alternative implementations, laser diode driver circuit 1114 can be bonded to a separate base substrate, such as in
Proximate the laser diodes 1110a, 1110b, 1110c, and 1110d there is positioned an optical director element 1118. Like the laser diodes 1110a, 1110b, 1110c, and 1110d, the optical director element 1118 is bonded to the top surface of the base substrate 1102. The optical director element 1118 may be bonded proximate to or adjacent each of the laser diodes 1110a, 1110b, 1110c, and 1110d. In the illustrated example, the optical director element 1118 has a triangular prism shape that includes a plurality of planar faces, similar to optical director element 118 in
The optical engine 1100a also includes a cap 1120 similar to cap 120 in
The optical director element 1118 is positioned and oriented to direct (e.g., reflect) laser light received from each of the plurality of laser diodes 1110a, 1110b, 1110c, and 1110d upward toward the optical window 1130 of the cap 1120, wherein the laser light exits the interior volume, similar to
The cap 1120 may have a round shape, rectangular shape, or other shape, similarly to as described regarding
The optical engine 1100a can also include four collimation/pointing lenses similarly to as discussed regarding
The optical engine 1100a may also include, or may be positioned proximate to, a beam combiner that is positioned and oriented to combine the light beams received from each of the collimation lenses or laser diodes 1110a, 1110b, 1110c, or 1110d into a single aggregate beam. As an example, the beam combiner may include one or more diffractive optical elements (DOE) and/or one or more refractive/reflective optical elements that combine the different color beams in order to achieve coaxial superposition. Exemplary beam combiners are shown and discussed with reference to
In at least some implementations, the laser diodes 1110a, 1110b, 1110c, 1110d, the optical director element 1118, and/or the collimation lenses may be positioned differently. As noted above, laser diode driver circuit 1114 may be mounted on a top surface or a bottom surface of the base substrate 1102, depending on the RF design and other constraints (e.g., package size). In at least some implementations, the optical engine 1100a may not include the optical director element 1118, and the laser light may be directed from the laser diodes 1110a, 1110b, 1110c, and 1110d toward collimation lenses without requiring an intermediate optical director element, such as illustrated in
Optical engine 1100a in
One skilled in the art will appreciate that the positions of laser diode driver circuitry 1114, electrical connections 1116a, 1116b, 1116c, 1116d, and electrically insulating cover 1140 as shown in
One difference between optical engine 1100b in
For implementations where laser diode drive circuit 1114 is not bonded to base substrate 1103a, electrical contacts 1117a, 1117b, 1117c, and 1117d could be bonded to base substrate 1103a, each at an end of a respective electrical connection 1116a, 1116b, 1116c, or 1116d as described above with regards to act 508 in
In some implementations, an optical engine similar to optical engine 700 may include a beam combiner 316 as described with regards to
The optical engine 1200a includes a base substrate 1202. The base substrate 1202 may be formed from a material that is radio frequency (RF) compatible and is suitable for hermetic sealing. For example, the base substrate 1202 may be formed from low temperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc. The optical engine 1200a also includes a plurality of laser diodes 1210a, 1210b, 1210c, 1210d bonded thereto. The plurality of laser diodes could include an infrared laser diode 1210d which provides infrared laser light 1238d, a red laser diode 1210a which provides red laser light 1238a, a green laser diode 1210b which provides green laser light 1238b, and a blue laser diode 1210c which provides blue laser light 1238c. Each of the laser diodes 1210a, 1210b, 1210c, and 1210d may comprise one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL), for example. For ease of illustration, each of the laser diodes in
Although not explicitly shown in
The optical engine 1200a also includes a cap 1220, which can be similar to cap 720 as discussed regarding
The cap 1220 may have a round shape, rectangular shape, or other shape. The optical window 1230 may comprise an entire side of the cap 1220, or may comprise only a portion thereof. In at least some implementations, the cap 1220 may include a plurality of optical windows instead of a single optical window 1230.
The optical engine 1200a can include four collimation/pointing lenses 1236a, 1236b, 1236c, and 1236d, one for each respective laser diode 1210a, 1210b, 1210c, and 1210d. Each of the plurality of collimation lenses 1236a, 1236b, 1236c, and 1236d can be positioned and oriented to receive light from a corresponding one of the laser diodes 1210a, 1210b, 1210c, and 1210d through the optical window 1230. In some implementations, each of the collimation lenses can be bonded to optical window 1230. In other implementations, the optical window 1230 can be formed to include each of the collimation lenses.
The collimation lenses 1236a, 1236b, 1236c, and 1236d couple the respective beams of light 1238a, 1238b, 1238c, and 1238d into respective optical elements 328, 330, 332, and 334 of a beam combiner 316. Beam combiner 316 in
In at least some implementations, at least some of the components may be positioned differently. As noted above, the laser diode driver circuit 1214 may be mounted on a top surface or a bottom surface of the base substrate 1202, or may be positioned remotely therefrom, depending on the RF design and other constraints (e.g., package size). In at least some implementations, the optical engine 1200a may include an optical director element (e.g., optical director element 118 of
Even though
For the sake of a controlled atmosphere inside the interior volume 1232, it may be desirable to have no organic compounds inside the interior volume 1232. In at least some implementations, the components of the optical engine 1200a may be bonded together using no adhesives. In other implementations, a low amount of adhesives may be used to bond at least one of the components, which may reduce cost while providing a relatively low risk of organic contamination for a determined lifetime (e.g., 2 or more years) of the optical engine 1200a. Similarly to as detailed above regarding
Due to the divergent beam from each of the laser diodes 1210a, 1210b, 1210c, and 1210d and the lateral distances between the laser diodes, the collimation lenses 1236a, 1236b, 1236c, and 1236d, and the beam combiner 316, it may be advantageous to minimize a distance between the respective output facets of the laser diodes 1210a, 1210b, 1210c, and 1210d and the optical window 1230. For the same reason, it may be advantageous to minimize the thickness of the optical window 1230 so that the collimation lenses 1236a, 1236b, 1236c, and 1236d can be positioned relatively close to the output facets of the laser diodes 1210a, 1210b, 1210c, and 1210d.
In at least some implementations, the collimation lenses 1236a, 1236b, 1236c, and 1236d may be actively aligned. In at least some implementations, the laser diodes 1210a, 1210b, 1210c, and 1201d, the cap 1220 (including optical window 1230), and/or the beam combiner 316 may be passively aligned.
In optical engine 1200b of
Throughout this application, collimation lenses have been represented in the Figures by a simple curved lens shape. However, the subject systems, devices, and methods can utilize more advanced collimation schemes, as appropriate for a given application.
The collimation schemes illustrated in
A person of skill in the art will appreciate that the teachings of the present systems, methods, and devices may be modified and/or applied in additional applications beyond the specific WHUD implementations described herein. In some implementations, one or more optical fiber(s) may be used to guide light signals along some of the paths illustrated herein.
The WHUDs described herein may include one or more sensor(s) (e.g., microphone, camera, thermometer, compass, altimeter, and/or others) for collecting data from the user's environment. For example, one or more camera(s) may be used to provide feedback to the processor of the WHUD and influence where on the display(s) any given image should be displayed.
The WHUDs described herein may include one or more on-board power sources (e.g., one or more battery(ies)), a wireless transceiver for sending/receiving wireless communications, and/or a tethered connector port for coupling to a computer and/or charging the one or more on-board power source(s).
The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Although specific embodiments of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be recognized by those skilled in the relevant art. The teachings provided herein of the various embodiments can be applied to other portable and/or wearable electronic devices, not necessarily the exemplary wearable electronic devices generally described above.
For instance, the foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, schematics, and examples. Insofar as such block diagrams, schematics, and examples contain one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, the present subject matter may be implemented via Application Specific Integrated Circuits (ASICs). However, those skilled in the art will recognize that the embodiments disclosed herein, in whole or in part, can be equivalently implemented in standard integrated circuits, as one or more computer programs executed by one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs executed by on one or more controllers (e.g., microcontrollers) as one or more programs executed by one or more processors (e.g., microprocessors, central processing units, graphical processing units), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of ordinary skill in the art in light of the teachings of this disclosure. When logic is implemented as software and stored in memory, logic or information can be stored on any processor-readable medium for use by or in connection with any processor-related system or method. In the context of this disclosure, a memory is a processor-readable medium that is an electronic, magnetic, optical, or other physical device or means that contains or stores a computer and/or processor program. Logic and/or the information can be embodied in any processor-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions associated with logic and/or information.
In the context of this specification, a “non-transitory processor-readable medium” can be any element that can store the program associated with logic and/or information for use by or in connection with the instruction execution system, apparatus, and/or device. The processor-readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device. More specific examples (a non-exhaustive list) of the computer readable medium would include the following: a portable computer diskette (magnetic, compact flash card, secure digital, or the like), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory), a portable compact disc read-only memory (CDROM), digital tape, and other non-transitory media.
The various embodiments described above can be combined to provide further embodiments. To the extent that they are not inconsistent with the specific teachings and definitions herein, at least the following are incorporated herein by reference in their entirety: U.S. Provisional Patent Application Ser. No. 62/438,725, U.S. Non-Provisional patent application Ser. No. 15/848,265 (U.S. Publication Number 2018/0180885), U.S. Non-Provisional patent application Ser. No. 15/848,388 (U.S. Publication Number 2018/0180886), U.S. Provisional Patent Application Ser. No. 62/450,218, U.S. Non-Provisional patent application Ser. No. 15/852,188 (U.S. Publication Number 2018/0210215), U.S. Non-Provisional patent application Ser. No. 15/852,282, (U.S. Publication Number 2018/0210213), U.S. Non-Provisional patent application Ser. No. 15/852,205 (U.S. Publication Number 2018/0210216), U.S. Provisional Patent Application Ser. No. 62/575,677, U.S. Provisional Patent Application Ser. No. 62/591,550, U.S. Provisional Patent Application Ser. No. 62/597,294, U.S. Provisional Patent Application Ser. No. 62/608,749, U.S. Provisional Patent Application Ser. No. 62/609,870, U.S. Provisional Patent Application Ser. No. 62/591,030, U.S. Provisional Patent Application Ser. No. 62/620,600, U.S. Provisional Patent Application Ser. No. 62/576,962, U.S. Provisional Patent Application Ser. No. 62/760,835, U.S. Non-Provisional patent application Ser. No. 16/201,664, U.S. Non-Provisional patent application Ser. No. 16/168,690, U.S. Non-Provisional patent application Ser. No. 16/171,206, U.S. Non-Provisional patent application Ser. No. 16/203,221, and/or PCT Patent Application PCT/CA2018051344. Aspects of the embodiments can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
Claims
1. An optical engine, comprising:
- a base substrate;
- a plurality of laser diodes, each of the plurality of laser diodes bonded directly or indirectly to the base substrate;
- at least one laser diode driver circuit operatively coupled to the plurality of laser diodes to selectively drive current to the plurality of laser diodes;
- a cap comprising at least one wall and at least one optical window that, together with the base substrate, define an interior volume sized and dimensioned to receive at least the plurality of laser diodes, the cap being bonded to the base substrate to provide a hermetic or partially hermetic seal between the interior volume of the cap and a volume exterior to the cap, and the optical window positioned and oriented to allow beams of light emitted from the plurality of laser diodes to exit the interior volume; and
- a photonic integrated circuit comprising a plurality of input facets and at least one output facet, in operation, the photonic integrated circuit receives a plurality of beams of light at the respective plurality of input facets and wavelength multiplexes the plurality of beams of light to provide an aggregated beam of light at the output facet.
2. The optical engine of claim 1, further comprising:
- a plurality of collimation lenses, each of the plurality of collimation lenses positioned and oriented to collimate light received from respective ones of the beams of light emitted from the plurality of laser diodes, and to output the collimated light toward the plurality of input facets of the photonic integrated circuit.
3. The optical engine of claim 2 wherein each of the plurality of collimation lenses is positioned within the interior volume.
4. The optical engine of claim 2 wherein each of the plurality of collimation lenses is bonded to the optical window of the cap.
5. The optical engine of claim 1 wherein the photonic integrated circuit is bonded to the optical window of the cap.
6. The optical engine of claim 1, further comprising an optical director element disposed within the interior volume, the optical director element bonded to the base substrate proximate the plurality of laser diodes, and positioned and oriented to reflect laser light from the plurality of laser diodes toward the optical window of the cap.
7. The optical engine of claim 6 wherein the optical director element comprises a mirror or a prism.
8. The optical engine of claim 1, further comprising:
- a collimation lens positioned and oriented to receive and collimate the aggregate beam of light from the output facet of the photonic integrated circuit.
9. The optical engine of claim 8 wherein the collimation lens comprises an achromatic lens or an apochromatic lens.
10. The optical engine of claim 1, further comprising at least one diffractive optical element positioned and oriented to receive the aggregate beam of light, in operation, the at least one diffractive optical element provides wavelength dependent focus correction for the aggregate beam of light.
11. The optical engine of claim 1, further comprising:
- a plurality of chip submounts bonded to the base substrate, wherein each of the laser diodes are bonded to a corresponding one of the plurality of chip submounts.
12. The optical engine of claim 1 wherein the plurality of laser diodes includes a red laser diode to provide a red laser light, a green laser diode to provide a green laser light, a blue laser diode to provide a blue laser light, and an infrared laser diode to provide infrared laser light.
13. The optical engine of claim 1 wherein the base substrate is formed from at least one of low temperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina, or Kovar®.
14. The optical engine of claim 1 wherein the at least one laser diode driver circuit is bonded to a first surface of the base substrate, and the plurality of laser diodes and the cap are bonded to a second surface of the base substrate, the second surface of the base substrate opposite the first surface of the base substrate.
15. The optical engine of claim 13 wherein the at least one laser diode driver circuit, the plurality of laser diodes, and the cap are bonded to a first surface of the base substrate.
16. The laser projector of claim 13 wherein the plurality of laser diodes and the cap are bonded to the base substrate, and the at least one laser diode driver circuit is bonded to another substrate separate from the base substrate.
17. The optical engine of claim 1 wherein each of the laser diodes comprises one of an edge emitter laser or a vertical-cavity surface-emitting laser (VCSEL).
18. The optical engine of claim 1 wherein the at least one wall of the cap comprises at least one continuous sidewall having a lower first end and an upper second end, the lower first end bonded to the base substrate, and the optical window is hermetically or partially hermetically sealed to the cap proximate the upper second end.
19. The optical engine of claim 1 wherein the photonic integrated circuit comprises a plurality of waveguides, each waveguide of the plurality of waveguides to receive laser light from a respective laser diode of the plurality of laser diodes.
20. The optical engine of claim 19, wherein each waveguide of the plurality of waveguides is optimized to receive and output laser light having a wavelength corresponding to the wavelength of laser light received from the respective laser diode.
21. The optical engine of claim 19 wherein the plurality of waveguides comprises a waveguide combiner.
22. The optical engine of claim 21 wherein the waveguide combiner comprises at least one of: a directional coupler, Y-branch, whispering gallery mode, or multi-mode interface coupler.
23. The optical engine of claim 19 wherein each waveguide of the plurality of waveguides includes an input facet to receive laser light from a respective laser diode of the plurality of laser diodes and an output facet to output the received laser light, a spacing between the output facets of each waveguide being smaller than a spacing between the input facets of each waveguide.
24. The optical engine of claim 1 wherein each input facet of the plurality of input facets is a grating input coupler.
25. The optical engine of claim 1 wherein each input facet of the plurality of input facets is a planar region with an index of refraction lower than an index of refraction of material from which the photonic integrated circuit is formed.
Type: Application
Filed: Dec 11, 2018
Publication Date: Jun 27, 2019
Inventors: Jörg Pierer (Alpnach), Rony Jose James (Alpnach), Stefan Mohrdiek (Affoltern am Albis), Douglas R. Dykaar (Waterloo)
Application Number: 16/216,899
