Abstract: A super luminescent light emitting diode includes an active waveguide that is grown using selective area epitaxy, a resistance array, and a contact pad. The active waveguide has a varying bandgap due to a width of the mask that is used for growing the active waveguide. The active waveguide is injected with varying current at each longitudinal section of the active waveguide due to varying resistance associated with the resistance array at each longitudinal section. The varying current is injected by the contact pad. The contact pad is a single continuous electrode. The varying bandgap and varying current at each longitudinal section of the active waveguide enable emission of optical light by each section of the active waveguide such that a combination of all the emitted light leads to emission of a super-broadband continuous spectrum and tailorable spectrum profile of the optical light.

Abstract: A photonic integrated circuit (PIC) includes various mode field adapters (MFAs), a waveguide, and various contact pads. All the MFAs are on a same facet of the PIC. One MFA of the PIC outputs a first optical signal that is an amplified version of a second optical signal. The waveguide is divided into two waveguide arms and a bend portion to join the two waveguide arms. The waveguide extends between the MFAs such that the second optical signal propagates through the waveguide. Further, each waveguide arm is formed between the contact pads. The second optical signal propagating through the waveguide is amplified based on a current that is injected in the PIC by way of the contact pads.

Abstract: The invention provides a method of growing semiconductor epitaxial layers on a substrate comprising the steps of providing a substrate, providing at least a first growth solution and optionally one or more further growth solutions, and (i) exposing the substrate to the first growth solution, the growth solution being under a supersaturated condition such that a first layer grows on the surface of the substrate; and, (ii) optionally exposing the substrate to one or more further growth solutions, the further growth solutions being under a supersaturated condition such that one or more further layers grow on the surface of the first layer; and (iii) varying the pressure of the system to change the degree of supersaturation of the first growth solution or one or more further growth solutions to affect the growth of the first layer or one or more further layers.

Abstract: A device for optical space switching in optical networks. The optical device comprises a broad area optical waveguide section having a number of electrodes extending over at least a portion of the length of the broad area optical waveguide section. The application of an electrical signal to an electrode causes a local change in effective refractive index of the broad area optical waveguide section, thereby causing light preferentially to propagate along a predetermined path in dependence on the configuration of the electrode. In particular the broad area waveguide device is implemented in indium phosphide (InP). Also described is a method for waveguiding in the optical device.

Abstract: The present invention relates to a semiconductor optical tap comprising: a multimode interferometer (MMI) (6); an input waveguide (1) coupled to the MMI; a first output waveguide (2) coupled to the MMI; and a second output waveguide (3) coupled to the MMI. The first and second output waveguides (2,3) overlap (d) such that unequal portions of light are coupled from the MMI into the first and second output waveguides (2,3). The input waveguide (1) and the first and second output waveguides (2,3) may have a rib structure. They may also be adiabatically tapered waveguides. The first and second output waveguides (2,3) may have different starting widths.

Abstract: The present invention relates to a semiconductor photodetector. The photodetector is a waveguide photodetector, which comprises: a waveguide (1,2,3) having a III-V ridge structure including an active layer (1); a semiconductor layer (4) deposited on top of the ridge structure; and, metal detector electrodes (not shown) on the surface of the higher refractive index semiconductor layer (4). The semiconductor layer (4) has a higher refractive index than the waveguide structure (1,2,3). The ridge structure is configured to widen along the length of the waveguide (1,2,3) such that light passing through the active layer (1) of the waveguide couples more efficiently up into the higher refractive index semiconductor layer (4).

Abstract: We propose a technique for fabricating stacked photonic lightwave circuits (PLCs), with both high and low refractive index steps, comprising the use of etched PECVD dielectric layers for the light guiding structures and which are surrounded and separated by an interlayer PLC cladding (IPC) comprising a non-conformal layer of sol-gel, whose composition, refractive index and thickness can be tailored to the requirements of the device.

Abstract: The layer structure of a DC-PBH laser diode consists of an n-InP substrate (51), an n-InP buffer layer (52), an undoped-InGaAsP active layer (53), a p-Inp cladding layer (54), a p-InP current blocking layer (55), an n-InP current blocking layer (56), a p-InP cladding layer (57), and a p-InGaAsP contact layer (58). An additional layer of Fe-doped InP layer (55a) creates an acceptor level (Fe3+/Fe2+) near mid-band gap. The iron impurities are deep level traps, and will make the capacitance C2 less dependent of the impurity concentration of layer (56) which is normally doped with a concentration larger than 1×1018 cm−3 to lower the leakage current from p-InP blocking layer (57) to p-InP blocking layer (55) that does not contribute to light emission. The capacitance C2 and hence the overall capacitance Cp-n-p-n will be reduced with this Fe doped InP layer (55a) and consequently the displacement current through the current blocking structure during high speed operation will be lowered.

Abstract: There is provided a semiconductor laser comprising a gain section and an adjacent Bragg section, wherein output laser light is emitted via a facet at an interface between air and the gain section, the Bragg section comprising a distributed reflecting structure having a length substantially greater than required to ensure single longitudinal mode operation of the laser in which the side-mode suppression ratio (SMSR) is 35 dB or more, thereby in use substantially suppressing optical feedback from a facet at an interface between the Bragg section and air, and wherein an interface between the Bragg section and the gain section is quantum well intermixed, thereby rendering the interface substantially anti-reflecting at the wavelength of the laser.

Abstract: A wavelength locked tunable laser source comprising a tunable laser source, an optical reference source characterized by a frequency spectrum with two combs of discrete components of different spacing, an optical mixing device and feedback control circuitry. An optical output of the laser source is heterodyned with an output of the optical reference source at the optical mixing device to produce an electrical signal in dependence on a difference beat frequency of the two optical outputs, the feedback control circuitry being operative to process the electrical signal to provide a feedback signal which is used to tune the wavelength of the laser source so as to minimize the beat frequency and thereby substantially lock the wavelength of the laser source to a wavelength in the spectrum of the optical reference source. The use of an optical reference source with a spectrum comprising two frequency combs provides a mechanism for determining the absolute frequency to which the laser has been locked.

Abstract: A pumping module for use in a solid state laser comprises an annular array of laser diode segments (10) forming a passage (24), each segment (10) comprising an extended body supporting a laser diode array (17) that extends along the longitudinal axis of the segment (10) for directing light into the passage (24) from an inner face (12) of the annular array, wherein adjacent side faces of any two segments (10) in the annular array are in sealing engagement. The inner faces (12) of the array of segments (10) form a continuous surface so that coolant can flow between a laser rod and the segments (10) to reduce localized heating.

Abstract: The present invention relates to a receiver for an infrared wireless communications system. The receiver comprises: a hot-spot monitoring photodetector array (6); a sensing photodetector array (7); an optical element (5) for splitting a received signal into two parts and focusing each part onto one of the photodector arrays (6, 7); means for monitoring the hot-spot monitoring photodetector array (6); and means for adjusting the response of the sensing photodetector array (7) in response to the detected signal of the hot-spot monitoring photodetector array (6).

Abstract: A wavelength locked tunable laser source comprising a tunable laser source, an optical reference source characterized by a frequency spectrum with two combs of discrete components of different spacing, an optical mixing device and feedback control circuitry. An optical output of the laser source is heterodyned with an output of the optical reference source at the optical mixing device to produce an electrical signal in dependence on a difference beat frequency of the two optical outputs, the feedback control circuitry being operative to process the electrical signal to provide a feedback signal which is used to tune the wavelength of the laser source so as to minimize the beat frequency and thereby substantially lock the wavelength of the laser source to a wavelength in the spectrum of the optical reference source. The use of an optical reference source with a spectrum comprising two frequency combs provides a mechanism for determining the absolute frequency to which the laser has been locked.

Abstract: The present invention relates to a semiconductor photodetector. The photodetector is a waveguide photodetector, which comprises: a waveguide (1,2,3) having a III-V ridge structure including an active layer (1); a semiconductor layer (4) deposited on top of the ridge structure; and, metal detector electrodes (not shown) on the surface of the higher refractive index semiconductor layer (4). The semiconductor layer (4) has a higher refractive index than the waveguide structure (1,2,3). The ridge structure is configured to widen along the length of the waveguide (1,2,3) such that light passing through the active layer (1) of the waveguide couples more efficiently up into the higher refractive index semiconductor layer (4).

Abstract: The present invention relates to a semiconductor optical tap comprising: a multimode interferometer (MMI) (6); an input waveguide (1) coupled to the MMI; a first output waveguide (2) coupled to the MMI; and a second output waveguide (3) coupled to the MMI. The first and second output waveguides (2,3) overlap (d) such that unequal portions of light are coupled from the MMI into the first and second output waveguides (2,3). The input waveguide (1) and the first and second output waveguides (2,3) may have a rib structure. They may also be adiabatically tapered waveguides. The first and second output waveguides (2,3) may have different starting widths.

Abstract: The present invention provides a novel technique based on gray scale mask patterning (110), which requires only a single lithography and etching step (110, 120) to produce different thickness of SiO2 implantation mask (13) in selected regions followed by a one step IID (130) to achieve selective area intermixing. This novel, low cost, and simple technique can be applied for the fabrication of PICs in general, and WDM sources in particular. By applying a gray scale mask technique in IID in accordance with the present invention, the bandgap energy of a QW material can be tuned to different degrees across a wafer (14). This enables not only the integration of monolithic multiple-wavelength lasers but further extends to integrate with modulators and couplers on a single chip. This technique can also be applied to ease the fabrication and design process of superluminescent diodes (SLDs) by expanding the gain spectrum to a maximum after epitaxial growth.

Abstract: According to the present invention, a travelling-wave electroabsorption modulator (TW-EAM) comprises: an optical waveguide with a plurality of adjacent regions electrically isolated from each other, the regions being characterized alternately by the properties of electroabsorption (EA) and optical transparency over the same range of optical wavelengths, and a microwave transmission line located above the optical waveguide, such that sections of the transmission line located above EA regions in the optical waveguide are in electrical contact with said EA regions, whereas sections of the transmission line located above transparent regions in the optical waveguide are electrically isolated from said transparent regions.

Abstract: A device for optical space switching in optical networks. The optical device comprises a broad area optical waveguide section having a number of electrodes extending over at least a portion of the length of the broad area optical waveguide section. The application of an electrical signal to an electrode causes a local change in effective refractive index of the broad area optical waveguide section, thereby causing light preferentially to propagate along a predetermined path in dependence on the configuration of the electrode. In particular the broad area waveguide device is implemented in indium phosphide (InP).

Abstract: There is provide an optical device comprising a planar structure adapted so that light coupled into an optical layer of the device follows a folded optical path, thereby increasing the interaction length, wherein the folded optical path is substantially perpendicular to the planar structure so as to render the optical device substantially polarization insensitive. Typically, the folded path is achieved by modifying at least one of an upper surface of the optical layer and a lower surface of the optical layer such that it is no longer planar, but instead comprises one or more angled facets.

Abstract: In the present invention, there is provided an optical device comprising a multimode interference (MMI) optical waveguide section having a number of electrodes extending over at least a portion of the length of the MMI section, where the application of an electrical bias to an electrode causes a local change in effective refractive index of the MMI section, thereby causing light preferentially to propagate along a path defined by the configuration of said electrode. Whereas current injection has been demonstrated in the prior art, the present invention operates by the application of a reverse bias electric field, via suitably shaped electrodes, to locally increase the reflective index within part of the device. Thus the electrodes on the device are used to create new wave guiding paths, rather than to minimise mode coupling to crossover states, as is the case with prior art devices. The shape and extent of the induced waveguides can be controlled by the shape of the electrodes.