OPTICAL TRANSMITTER ASSEMBLY FOR VERTICAL COUPLING
The invention relates to an optical transmitter assembly (OTA) for vertical coupling of light into a chip, and to a method for manufacturing the OTA. The OTA includes a laser diode, a microlens and a turning mirror mounted at a top face of a supporting substrate within a sealed enclosure, and an optical component, such as an optical isolator, a polarizer, or a microlens disposed in a substrate cavity that opens to the back face of the substrate. The optical component may be placed into the cavity after the enclosure is sealed.
The present invention generally relates to optoelectronic circuits, and more particularly relates to an optical transmitter assembly for coupling light vertically into a planar integrated circuit.
BACKGROUNDSilicon-based integrated circuits incorporating planar optical waveguides and light processing elements such as optical modulators, receivers, attenuators, splitters, combiners, amplifiers etc. are being developed and used in a variety of applications. Examples of such circuits, which may be referred to as silicon photonics (SiP) chips, include optical interconnects and optical routers, among others. However, conventional silicon photonics (SiP) chips cannot generate light at typical optical communication wavelengths in the 1.3 μm and 1.55 μm ranges, so that light of these wavelengths has to be coupled into a SiP chip from an external laser, typically a semiconductor laser diode (LD) emitting at the desired wavelength. What is needed is an optical transmitter assembly that has a small footprint, protects the LD from the environment and back reflections, and is configured to couple light generated by the LD directly into a SiP chip at a desired location on the chip.
SUMMARYAccordingly, the present disclosure relates to an optical transmitter assembly (OTA) for vertical coupling of light into an integrated circuit (IC) chip, the OTA comprising a substrate, a laser diode, a turning mirror, and a polarization processing element, wherein the laser diode and the polarization processing element are disposed at opposing sides of the substrate, and wherein the turning mirror is configured to re-direct an optical path from the laser diode through the substrate and the polarization processing element. The polarization processing element may be disposed in a cavity in the supporting substrate.
In the context of this specification, “vertical coupling” means coupling light into a planar chip from a main face of the chip as opposed to coupling into an edge thereof, and is not limited to optical coupling at normal incidence.
One aspect of the present disclosure provides an optical transmitter assembly (OTA) comprising: a substrate having a first face and a second face opposing the first face; a laser diode (LD) disposed at the first face of the substrate and configured to emit a light beam along the substrate; a turning mirror provided at the first face of the substrate and configured to re-direct the light beam to propagate through the substrate emerging from the second face thereof; and a first microlens disposed between the LD and the turning mirror and configured to at least partially collimate or focus the light beam. The substrate includes a cavity that is open to the second face and positioned in an optical path of the light beam; the cavity is configured for placing therein a polarization processing or collimating optical element from the second face of the substrate. According to one feature of the present disclosure, the OTA may comprise one or more polarization processing optical components disposed within the cavity. According to another feature of the present disclosure, the OTA may comprise a microlens disposed within the cavity.
One aspect of the present disclosure provides an optical transmitter assembly (OTA) comprising: a substrate having a first face and a second face opposing the first face; a lid attached to the substrate so as to form an enclosure at the first face thereof; a laser diode (LD) mounted within the enclosure and configured to emit a light beam along the substrate; a turning mirror provided within the enclosure and configured to re-direct the light beam to propagate through the substrate into the CMOS chip when the OTA is mounted upon the CMOS chip at the second face; and a first microlens disposed within the enclosure optically between the LD and the turning mirror and configured to at least partially collimate or focus the light beam. The substrate includes a cavity positioned in an optical path of the light beam and configured for placing therein a polarization processing optical component from the second face of the substrate.
One aspect of the present disclosure provides an optical transmitter assembly (OTA) comprising: a substrate having a first face and a second face opposing the first face; a lid attached to the substrate so as to form an enclosure at the first face thereof; a laser diode (LD) mounted within the enclosure and configured to emit a light beam along the substrate; a turning mirror provided within the enclosure and configured to re-direct the light beam to propagate through the substrate into the CMOS chip when the OTA is mounted upon the CMOS chip at the second face; and a first microlens disposed within the enclosure optically between the LD and the turning mirror and configured to at least partially collimate or focus the light beam. A polarization processing optical component is disposed within a cavity in the substrate that opens to the second face of the substrate and is positioned in an optical path of the light beam.
One aspect of the present disclosure provides an optical transmitter assembly (OTA) comprising: a substrate having a first face and a second face opposing the first face; a lid attached to the substrate so as to form an enclosure at the first face thereof; a laser diode (LD) mounted within the enclosure and configured to emit a light beam along the substrate; a turning mirror provided within the enclosure and configured to re-direct the light beam to propagate through the substrate into the CMOS chip when the OTA is mounted upon the CMOS chip at the second face; a first microlens disposed within the enclosure optically between the LD and the turning mirror and configured to at least partially collimate or focus the light beam; and a second microlens disposed within a cavity in the substrate in an optical path of the light beam optically after the turning mirror.
Another aspect of the present disclosure provides a method of making an optical transmitter assembly (OTA), the method comprising:
a) providing a light source sub-assembly fixedly disposed at a first face of a substrate, the substrate having a cavity that is open to a second face of the substrate opposing the first face, the light source sub-assembly comprising a laser diode (LD) disposed at the first face of the substrate and configured to emit a light beam along the substrate, a turning mirror configured to direct the light beam through the substrate to be output from a second face of the substrate opposing the first face thereof, and a first microlens disposed between the LD and the turning mirror and configured to at least partially collimate or focus the light beam; and
b) placing a polarization processing or collimating optical element into the cavity from the second face in an optical path of the light beam.
The method may further comprise c) affixing a lid to the substrate at the first face thereof so as to form a sealed enclosure housing the light source sub-assembly. The sealed enclosure may be hermetic or may not be hermetic, as needed.
Embodiments disclosed herein will be described in greater detail with reference to the accompanying drawings which represent example embodiments thereof, in which like elements are indicated with like reference numerals, and wherein:
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular optical circuits, optical components, techniques, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods, devices, and circuits are omitted so as not to obscure the description of the present invention.
Note that as used herein, the terms “first”, “second” and so forth are not intended to imply sequential ordering, but rather are intended to distinguish one element from another unless explicitly stated. Similarly, sequential labeling of method steps or operations do not imply sequential order of their execution. The terms ‘polarization processing component’ and ‘polarization component’ are used herein interchangeably to refer to optical components whose effects on incident light depend substantially on the light's polarization, such as optical isolators, polarizers, polarization rotators, polarization beam splitters, and wave plates.
With reference to
The turning mirror 26 is located in the optical path of the light beam 99 at the first face 41 of the substrate 40. It is configured to re-direct the light beam 99 to propagate through the substrate 40 so as to emerge from the second substrate face 42 and couple into the SiP chip 61 when OTA 10a is mounted above or upon the SiP chip 61 with the second substrate face 42 proximate to a top face of the chip 61. The microlens 24 may be disposed optically between the LD 22 and the turning mirror 26 and configured to at least partially collimate or focus the light beam 99. The microlens 24, which may also be referred to herein as the first microlens, may be a ball lens or an aspheric lens, for example, and may be mounted, e.g. glued, in an opening 24 defined in the first substrate face 41. The substrate 40 includes a back cavity 44 that is positioned in the optical path of the light beam 99 where it traverses the substrate 40, and is configured for placing therein a polarization processing optical element from the second face 42 of the substrate 40. The back cavity 44 may be open at the second substrate face 42. In the illustrated embodiment, the back cavity 44 includes an optical isolator 30, configured to prevent deleterious back reflections into the LD 22 from the SiP chip 61. In one embodiment, the back cavity 44 is configured to receive the entire optical isolator 30, so that OTA may be mounted on the chip 61 flush with the top face thereof. In one embodiment, the entire optical isolator 30 may be slightly recessed into the cavity, for example a few micrometers or 10-50 micrometers, in order to reduce the likelihood of the isolator being damaged during handling.
Referring now to
Turning back to
The process of affixing the lid 11 to the substrate 40 may include heating the OTA 10a to an elevated temperature, for example up to 150-180 centigrade or greater, to seal the enclosure 21. Heating the optical isolator 30 to temperatures required for sealing the enclosure may damage the optical isolator 30, for example due to delatching of its constituent components, or it may be detrimental for the isolator performance. Advantageously, locating the optical isolator 30 in the back cavity 44 of the substrate 40 enables placing the optical isolator 30 after the lidding process is completed, and the OTA is cooled and tested, thereby substantially eliminating or at least reducing the danger of the isolator failure, and saving fabrication time. Furthermore, the isolator 30 located within the back cavity 44 that opens to the back face of the substrate may be replaced, when needed, without opening the lid 11, thereby reducing the possibility of accidental damage to the optical components within the enclosure 21. Furthermore, placing the isolator 30 in the back cavity 44 enables reducing the footprint of the OTA, and therefore lowering its cost. Furthermore, the optical isolator 30, which is a relatively expensive component, can be installed in only those OTAs that have passed required electro-optical tests, which saves fabrication time and further reduces the average cost of the final device.
Turning first to
With reference to
With reference to
Advantageously, locating a polarization component such as the HWP 33 or the polarizer 33 in the back cavity 44 of the substrate 40 enables adding that polarization component to the OTA after the lidding process is completed and OTA 10a is cooled and tested, thereby substantially eliminating or at least reducing the likelihood of damaging the polarization component placed in the back cavity 44, and saving time. Furthermore, the polarization component placed in the back cavity 44 may be replaced, when needed, without opening the lid 11, thereby reducing the possibility of an accidental damage to the optical components within the enclosure 21. Furthermore, placing the HWP 33 or the polarizer 32 in the opening 44 in the back face of the substrate 40 enables reducing the footprint of the OTA.
With reference to
With reference to
In the exemplary embodiments described hereinabove, the enclosure 21 is formed substantially by an opening within the lid 11 wherein the LD 22 and the microlens 24 are located; one of the walls of this opening may be inclined and coated to form the turning mirror 26. It will be appreciated, however, that any of the embodiments described hereinabove may be modified so that the turning mirror 26 is provided by an inclined wall formed within the substrate 40.
With reference to
With reference to
Referring now to
The above-described exemplary embodiments are intended to be illustrative in all respects, rather than restrictive, of the present invention. Thus the present invention is capable of many variations in detailed implementation that can be derived from the description contained herein by a person skilled in the art; all such variations and modifications are considered to be within the scope and spirit of the present invention as defined by the following claims. For example, although exemplary embodiments of the optical transmitter assembly of the present disclosure were described hereinabove primarily with reference to coupling light into silicon-based photonics chips, they may also be configured for other applications where vertical coupling of light may be useful. Furthermore, each of the exemplary embodiments described hereinabove may include features described with reference to other embodiments. For example the second microlens 124, which is described hereinabove with reference to OTA 10e of
Thus, the present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes.
Claims
1. An optical transmitter assembly (OTA)comprising:
- a single substrate having a first face and a second face opposing the first face;
- a laser diode (LD), disposed at the first face, configured to emit a light beam along the first face;
- a turning mirror, provided at the first face, configured to re-direct the light beam to propagate through the single substrate and emerge from the second face; and
- a first microlens, disposed between the LD and the turning mirror, configured to at least partially collimate or focus the light beam; wherein the single substrate includes a cavity that is located within the single substrate, open to the second face at a bottom portion of the single substrate, positioned in an optical path of the light beam, and configured to receive an optical component.
2. The OTA of claim 1, further comprising:
- a lid, attached to the single substrate at the first face, configured to form an enclosure for enclosing the LD, the first microlens, and the turning mirror.
3. The OTA of claim 1, further comprising,
- one or more polarization processing optical components disposed within the cavity and in the optical path of the light beam.
4. The OTA of claim wherein the one or more polarization processing optical components include one or more of an optical isolator, a half-wave plate, or a polarizer.
5. The OTA of claim 1, further comprising:
- a non-reciprocal polarization rotator disposed optically between the LD and the turning mirror.
6. The OTA of claim 5, wherein at least one of the first microlens or the non-reciprocal polarization rotator is recessed into the first face.
7. The OTA of claim 1, wherein the first microlens comprises an aspheric lens.
8. The OTA of claim 1, further comprising:
- a second microlens, disposed optically after the turning mirror, configured to shape the light beam prior to egress from the OTA.
9. The OTA of claim 8, wherein the second microlens is disposed in the cavity.
10. The OTA of claim 8, wherein the second microlens is aspheric.
11. The OTA of claim 2, wherein the LD and the first microlens are mounted upon the first face, and the turning mirror comprises an inclined surface formed in the lid.
12. A method of making an optical transmitter assembly (OTA), the method comprising:
- providing a light source sub-assembly fixedly disposed at a first face of a single substrate, the single substrate having a cavity that is located within the single substrate and open to a second face of the single substrate opposing the first face, the second face being located at a bottom portion of the single substrate, and the light source sub-assembly comprising: a laser diode (LD), disposed at the first face, configured to emit a light beam along the first face; a turning mirror configured to direct the light beam through the single substrate to be output from the second face; and a first microlens, disposed between the LD and the turning mirror, configured to at least partially collimate or focus the light beam; and
- placing a polarization processing or collimating optical element into the cavity and in an optical path of the light beam.
13. The method of claim 12, further comprising:
- affixing a lid to the single substrate to form a sealed enclosure housing the light source sub-assembly at the first face.
14. The method of claim 13, further comprising:
- testing, after affixing the lid, an ability of the light source sub-assembly to generate light.
15. The method of claim 13, wherein
- the lid is affixed by heating the OTA to an elevated temperature, and
- the polarization processing or collimating optical element is placed into the cavity when the single substrate is cooled.
16. The method of claim 12, wherein the polarization processing or collimating optical element includes one or more of an optical isolator, a half-wave plate, or a polarizer.
17. The method of claim 12, further comprising:
- placing a second microlens into the cavity and in the optical path of the light beam.
18. The method of claim 12 wherein providing the light source sub-assembly comprises:
- providing a non-reciprocal polarization rotator between the LD and the turning mirror wherein the first microlens and the non-reciprocal polarization rotator are recessed into the first face.
19. The OTA of claim 1, wherein the first microlens comprises a ball lens.
20. An optical transmitter assembly (OTA) for coupling light into an integrated circuit chip, the OTA comprising:
- a single supporting substrate;
- a laser diode;
- a turning mirror; and
- a polarization processing element,
- wherein the laser diode and the polarization processing element are disposed at opposite faces of the single supporting substrate,
- wherein the turning mirror is configured to re-direct an optical path from the laser diode through the single supporting substrate and the polarization processing element, and
- wherein the polarization processing element is disposed in a cavity in the single supporting substrate,
- the single supporting substrate being located within the cavity and the cavity being open to a face, of the opposite faces, at a bottom portion of the single supporting substrate.
Type: Application
Filed: Jul 15, 2015
Publication Date: Jan 19, 2017
Inventors: Claude GAMACHE (Gatineau), Nicolas BELANGER (Gatineau), Scott CAMERON (Ottawa)
Application Number: 14/800,417