Abstract: In the present invention, profiling of the end facet of an optical waveguide reduces the amount of reflected light propagating in the waveguide. In a conventional waveguide, the effective reflectivity experienced by light at a facet is determined by the modal content of the light and the refractive index of the waveguide (core and cladding) and other material at either side of the dielectric interface, which constitutes the facet. In the present invention, depending upon the modal content of the light, the waveguide dimensions and the refractive indices at the dielectric interfaces, we adjust the profile of the facets so that it is no longer planar and so substantially reduce the amount of reflected light propagating back along the waveguide. This reduction in “effective reflectivity” can be due to an increase in the loss experienced by any reflected light or due to an increase in the amount of light transmitted.

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: 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: 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 invention provides a method of growing semiconductor epitaxial layers on a substrate comprising the steps of

Abstract: In a method of manufacturing a photonic integrated circuit having a compound semiconductor structure having a quantum well region, the structure is irradiated using a source of photons to generate defects, the photons having energy (E) at least that of the displacement energy (ED) of at least one element of the compound semiconductor. The structure is subsequently annealed to promote quantum well intermixing. The preferred radiation source is a plasma generated using an electron cyclotron resonance (ECR) system. The structure can be masked in a differential manner to selectively intermix the structure in a spatially controlled manner by controlling the exposure portions of the structure to the source of radiation.

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.