Abstract: An electro-optic modulator having a continuously adjustable chirp is provided. Optical signals input into the electro-optic modulator are divided into portions which are phase modulated in opposite senses, one portion imparted with a positive chirp and the other with a negative chirp. Variable couplers are used to adjust (by way of adjusting their coupling ratios) the amount of power allocated between the optical signals contributing to the positive chirp and the power of signals contributing to the negative chirp so that when the optical signals are combined an optical signal with an adjustable chirp is produced.

Abstract: A compact source capable of generating continuously tunable high frequency microwave radiation and short optical pulses in the picosecond/sub-picosecond range is invented. It includes a laser structure having two lasers formed on the same substrate which simultaneously operate at different longitudinal modes. Each laser has a complex coupled (gain-coupled or loss-coupled) grating which is formed by deep etching through a multi-quantum well structure, either of the active medium or of the additional lossy quantum-well layers, thus ensuring no substantial interaction between lasers. The lasers have a common active medium and shared optical path and provide mutual light injection into each other which results in generation of a beat signal at a difference frequency of two lasers. The beat frequency is defined by spacing between the laser modes and may be continuously tuned by current injection and/or temperature variation. Thus, the beat signal provides a continuously tunable microwave radiation.

Abstract: Disclosed is a print quality test structure for devices manufactured by lithography. The test structure allows for visual inspection of the print quality of the device. The test structure decouples the effects of overexposure, underexposure and focus so that corrections can be made for future device manufacturing. By visually inspecting each device during lithography, devices of poor quality can be reworked, and costly testing on all devices can be avoided through device screening.

Abstract: An assembly for combining the outputs from a group of n single mode optical fibres on to the photosensitive surface of a photodetector (1) has an adiabatically tapered bundle (2) of fibres (3) the small end of which is fusion spliced to one end of a length (4) of multimode fibre whose other end is optically coupled with the detector (1) by means of a lens (5).

Abstract: An isolation device that can be used for providing optical and electrical isolation between areas of an integrated chip. The isolation device includes three doped elongate regions which form diodes which can be connected in series. The isolation device can be used in optical devices or optical attenuators.

Abstract: An optical amplifier is constituted by a planar waveguide having an optical core intersected by a transverse trench occupied by a polymeric optically amplifying medium. An optical pump for the amplifier is provided by a laser diode positioned to direct its emission, transversely with respect to the waveguide axis, into the polymer.

Abstract: A method of controlling birefringence in a rib waveguide structure manufactured in silicon is describes. The rib waveguide structure comprises an elongated rib element having an upper face and two side faces. According to the method, a blanket layer of silicon nitride is formed to a predetermined thickness over the rib waveguide structure directly abutting the upper face and side faces. The thickness of the blanket layer is selected to control birefringence. A silicon rib waveguide structure incorporating such a layer and a evanescent coupler structure are also described.

Abstract: A doped slab region is described for use around a ridge waveguide, for controlling the refractive index of the waveguide material. Instead of simply diffusing dopant in from a surface of the slab region adjacent the waveguide, an area of the slab region is etched and dopant diffused in from a side face of the etched region. Thus, the dopant profile is established from a horizontal direction, allowing the profile to be controlled. A simple vertically uniform doping profile can thus be provided, leading to a vertically uniform current density, or an anisotropic wet etch can be applied after the initial etch to provide a profile which concentrates the current density at a selected height in the slab region.

Abstract: An integrated optical package comprises an integrated optical device supported on a carrier with a gelatinous material therebetween to assist in heat conduction. The carrier can include a thermal regulating device such as a heat sink or heater for regulating the temperature of the integrated optical device via the gelatinous material. The gelatinous material can include a metallic second phase suspended in the gelatinous material, to improve its thermal conductivity. The maximum dimension of the particles is ideally smaller than the gap between the integrated optical device and the carrier in which the gelatinous material is located, such as in the 5 to 95 percent range of the dimension of the gap. The particles of the metallic second phase can be elongate, in which case they can be aligned with each other such as in a direction extending from the integrated optical device towards the carrier. Alternatively, they can be substantially spherical.

Abstract: A dispersive optical waveguide array comprises a plurality of waveguide sections forming optical paths in parallel, each of the curved sections having the same curvature and the same section length around the curve.

Abstract: An external cavity laser comprises a light source unit, preferably comprising a semiconductor light source having internal optical gain and a collimating lens, for supplying substantially collimated light to a retroreflector via an angle-tuned filter extending across an optical axis of the light source. The retroreflector is positioned so as to receive light from the light source via the angle-tuned filter and reflect the light via the angle-tuned filter back to the light source. The retroreflector may comprise a quarter pitch graded-index (GRIN) lens having a proximal end surface oriented towards the light source and a distal end surface opposite thereto, with a mirror provided on the distal end surface, preferably as a high-reflectance coating. The angle-tuned filter may be attached to the proximal end surface of the GRIN lens, preferably as a coating. The GRIN lens may be tilted in order to vary the angle of the filter relative to the optical axis and hence the wavelength.

Abstract: A rib waveguide structure comprising a layer (4) of light conductive material defined between two planar faces with a rib (9) formed on one of the faces and an optical component e.g. a tapered waveguide (6) optically coupled to the other face. An inverted rib waveguide comprising a light conductive layer (11) and a rib (10) that projects from the light conductive layer (11) into a substrate (4,8) is also described as well as other optical devices comprising a light conductive layer separated from a substrate by a non-planar layer (3) of light confining material and optical devices comprising two or more layers (2, 3; 18, 19, 20) of light confining material buried within a rib with a light conducting component (10; 17; 22) at least a part of which is formed between planes defined by the two layers of light confining material. A method of forming such devices is also described.

Abstract: An optical fiber amplifier or laser comprises an optical housing having a diffusive reflective inner surface and at least one opening for receiving pump light. An optical fiber having a doped core is at least partially contained within the optical housing. The optical fiber can be pumped by an optical source without the need for any complex or expensive optical couplers. Lateral illumination of the fiber core with pump light enables many fibers to be pumped by the same pump source, so that a separate dedicated coupler is no longer required to couple the pump light into each optical cable.

Abstract: An improved method for etching a pattern in a semiconductor material is based on the formation of an InP grating mask on the semiconductor material. The formation of the InP grating mask involves the formation of a multi-layered structure on the semiconductor material with an etch-stop layer between two InP layers. A photoresist grating mask corresponding to the pattern to be etched in the semiconductor material is then formed on the top InP layer. Subsequently, a non-selective etch is used to penetrate the top InP layer, the etch-stop layer, and the lower InP layer. A suitable stripping solvent is then used to remove the photoresist followed by a selective etch to clear the remaining exposed InP material, remove contaminated material and to expose the underlying semiconductor material in accordance with the pattern to be etched. Additional masking beyond the InP mask is, therefore, not required.

Abstract: A system for detecting an optical output at a predetermined frequency, the system comprising: a plurality of optical guides for introducing an optical signal at said frequency into an input end of a dispersive optical component at each of a plurality of introduction sites corresponding to said optical guides; a detector located at the output end of the dispersive optical component and arranged to detect the optical power level of the optical signal introduced at each introduction site; means for establishing an optical power profile by interpolation of the optical power levels; and selection means for selecting the input optical guide at the introduction site at which the generated optical power level is spatially closest to the peak of the optical power profile.

Abstract: A thermo-optic semiconductor device has one semiconductor region providing an optical waveguide and an adjacent semiconductor region providing a resistive heater between two doped regions, current may be passed through the resistive heater within the adjacent semiconductor region to heat it and thereby vary the optical characteristics of the waveguide.

Abstract: A two-stage circuit configured to control the temperature of a device, having: a first stage connected to the device for controlling the temperature of the device; and a second stage having a temperature sensor and a heat source associated with the first stage for controlling the temperature of the first stage. An apparatus and method for controlling the temperature of an optical, electrical, or electronic device, or other analogous device provides a greater degree of control, i.e. control within a narrower band than is currently possible, by utilising a second stage of control associated with the first stage of control.

Abstract: An optical device (110) has a substrate (101) with an outer surface (103) and an optical component (117) having a base (115) which interfaces with the outer surface of the substrate. In one embodiment at least one gap (109) is disposed between the outer surface of the substrate and the base of the optical device, the at least one gap containing an adhesive (125) which adheres the substrate and the optical device together and at least one interface (123,133) between the base and the outer surface. In another embodiment a plurality of spaced-apart gaps are disposed between the outer surface of the substrate and the base of the optical device, each gap containing an adhesive which adheres the substrate and optical device together.

Abstract: The invention relates to compound cavity optical reflection modulation laser system providing frequency modulation of laser light by phase induced effective reflection modulation of the laser rear facet. The system includes a single mode gain coupled DFB laser integrated with a passive waveguide section to form a compound cavity modulation system. The waveguide includes a multiple quantum well region which is reverse biased to utilize the quantum Stark effect for voltage controlled refractive index modulation, thus providing phase modulation of the laser light. The phase modulated light is fed back to the laser to interfere with the light generated within the laser and to form the output light generated from the compound cavity. The interference effects cause modulation of the effective complex reflection of the rear laser facet which results in frequency modulation of the output light.

Abstract: A method of manufacturing an integrated optical device on a substrate is described wherein the device comprises first and second areas each containing at least one optical component. The first and second areas are separated by a third relatively featureless area, which provides optical communication between the first and second areas. The method uses a photolithographic stepper to define features of the optical components in the first area within a first exposure field and the features of the optical component(s) in the second area within a second exposure field, the stepper being moved between exposures so that first and second exposure fields are contiguous, and a line of contact or area of overlap between the first and second fields lies within the third, relatively featureless area of the substrate.