Abstract: A tuneable laser includes a gain section bounded at one end by a first reflector adapted to produce a comb of reflective peaks and on the other end by a second reflector in the form of a plurality of discrete grating units each capable of reflecting at one of the peaks of the comb, and each grating unit having at least two independently actuable electrodes, which when actuated independently one from the other is capable of reducing the reflectivity of the grating unit and in which at least two of the grating units have different pitches.

Abstract: The invention relates to the stabilization of high power semiconductor laser diode sources as they are extensively used in the field of optical communication. Such lasers are mostly employed as so-called pump laser sources for fiber amplifiers, e.g. erbium-doped fiber amplifiers, and are designed to provide a narrow-bandwidth optical radiation with a stable power output in a given frequency band. To improve the wavelength locking range of such laser sources when operating without an active temperature stabilizing element, an external reflector providing very high relative feedback is used. The reflectivity bandwidth of the external reflector is broadened for improving the stability of the laser source. In commonly employed optical fibers for conducting the laser beam, the external reflector is formed by one or a plurality of appropriately designed fiber Bragg gratings.

Abstract: An optical pulse train generator (2) for use in the transmission of high speed optical data in a return-to-zero (RZ) signalling format is described.

Abstract: A tuneable laser having an active section, a phase section and a Bragg reflector comprising a plurality of descrete grating units, at least two of which gratings have a discrete pitch, wherein at least two of the gratings having a different pitch are each provided with a plurality of independently actuable electrodes.

Abstract: The invention relates to high power semiconductor diode lasers of the type commonly used in opto-electronics, mostly as so-called pump lasers for fiber amplifiers in the field of optical communication, e.g. for an erbium-doped fiber amplifier (EDFA) or a Raman amplifier. Such a laser, having a single cavity and working in single transverse mode, is improved by placing a multilayer large optical superlattice structure (LOSL) into at least one of the provided cladding layers. This LOSL provides for a significantly improved shape of the exit beam allowing an efficient high power coupling into the fiber of an opto-electronic network.

Abstract: A Mach-Zehnder interferometer modulator for modulating a beam of laser light includes a pair of separate waveguides through which the laser light is passed after splitting in a splitting zone and after which the light is recombined in a merge zone. The waveguides are formed in a semiconductor material with one of the electrodes of each pair being formed in a doped layer while the other electrode, the top electrode, is a surface metalisation. The doped layer is trenched so that adjacent electrodes in the doped layer are electrically isolated from one another so that one of the electrodes in the doped layer can be connected with a different electrical polarity to the other electrode in the doped layer thereby permitting the connection of the pairs of electrodes in parallel anti-phase mode.

Abstract: An EDF amplifier comprises two EDF loops separated by optical isolators and pumped with light by pump laser diodes under the control of an output power control system. To achieve the required output power the current supplied to the pump supplying light to the input loop is set to the maximum drive current Imax for the pump laser, and the pump currents of all pumps not supplying light to the input loop, that is the pumps supplying light to the further loop or loops, are adjusted to achieve the required output power. To avoid a very high MPI, the inversion of all loops is never so low that the gain in the first loop has to compensate for loss in the following loop or loops. This is done by providing a minimum pump power to the second loop and any following loops. This ensures that the loops are always inverted enough, and that they do not exhibit too much loss. The required minimum pump current is obtained by modelling and experimental verification.

Abstract: The invention is concerned with a method f alignment for aligning crystal planes of a wafer substrate (40) to lithographic features thereon, the method characterized in that it includes the steps of: (a) measuring angular orientation of a peripheral flat (200) of the substrate (40); (b) measuring a crystallographic plane orientation of the substrate (40); (c) determining an error angle (?) between the annular orientation of the flat (200) and the crystallographic orientation; (d) angularly registering to the flat (200) in a lithographic tool; (e) rotating the substrate (40) by the error angle (?); and (f) defining one or more feature layers on the substrate (40) using the lithographic tool, thereby angularly aligning the one or more feature layers to the crystallographic plane orientation.

Abstract: An optical fibre is secured to an electronic package (10) by, firstly, providing in a wall (14) of the package (10) an electrically conductive tube (12), an inductance arrangement (16–22) in magnetically co-operational relation to the tube (12) and a securing agent inside the tube, then secondly inserting the fibre into the tube (12) and passing an RF current through the inductance arrangement (16). The current is such as to melt the securing agent and, when the securing agent is allowed to cool, a bond is formed between the fibre and the tube (12). The package (10) is preferably an LTCC mulilayer package with the inductance (16) being formed in adjacent layers and the tube (12) is preferably composed of a metallic ink which is applied to a stepwise-circular cylindrical cavity likewise formed in adjacent layers.

Abstract: A composite waveguide termination structure including two different waveguide conductor geometries operatively located upon a common substrate, wherein each such waveguide geometry includes a ground conductor on the same surface of the substrate.

Abstract: A method for integrating optical devices in a single growth step by utilizing a combination of Selective Area Growth and Etch (SAGE) is provided. An first device is formed between a set of oxide-masked regions, whilst a second device is formed in an adjacent planar region. By use of Selected Area Growth and Etch (SAGE), in which the growth between the oxide-masked regions is greater than the growth in the planar region, and in which the etch rate in the area between the oxide-masked regions is substantially the same as that in the planar region, the number of active quantum layers for the first device are formed between the oxide-masked regions, and a different number of layers for the second device is formed in the planar region.

Abstract: A semiconductor optical wave guide device (1) comprising a semiconductor layer (3) having an upper surface (5), and a lower surface (7) which is defined by a lower confinement layer(9), the semiconduct or layer having formed therein: (a) a wave guide (13); (b) at least one recess (19) adjacent to the waveguide (13)and extending from the upper surface (5)of the semiconductor layer (3); (c) at least one doped region (21, 23), at least part of which is situated between a said recess (19) and the lower confinement layer (9); and (d) at least one trench (25) adjacent to a said doped region (21, 23) and recess (19) and situated on an opposite side thereof to the waveguide, wherein the (or each) trench (25) extends from the upper surface of the semiconductor layer (3).

Abstract: An asymmetric MEMS thermal actuator device includes a base portion, typically a pair of bond pads, and an actuator element connected to the base portion by a flexure portion. The actuator element has a first arm and a second arm alongside the first arm and spaced from the first arm. The second arm is wider than the first arm so that the actuator element deflects about the flexure element due to differential heating in the first and second arms when an electrical current is passed therethrough. A cut-out portion is provided in the second arm adjacent the first arm so as to increase the spacing therefrom over at least a portion of the second arm. Preferably, a heat sink is also provided laterally adjacent the second arm.

Abstract: An Optical communications apparatus, comprising: (a) an optical integrated device comprising an input, one or more integrated optical component(s) and an output, arranged such that light received by the input is propagated by the optical component(s) and exits the device as an output light beam; (b) a light beam diverter arranged to divert a sample portion only of the power of the output light beam; (c) a light detector arranged to detect the sample portion of the output light beam; and (d) a polariser located between the light beam diverter and the light detector and/or between the output of the optical integrated device and the light beam diverter, the polariser being arranged such that if light of a predetermined polarisation is received by the optical integrated device, the polariser propagates light of that polarisation only, thereby substantially to prevent light other than of the predetermined polarisation being detected by the light detector.

Abstract: An optical device, including a monolithically integrated diode laser and semiconductor optical amplifier, that has reduced linewidth and improved side mode suppression for a given output power target. In a preferred embodiment, the diode laser is detuned from a gain peak wavelength to an emission wavelength. The semiconductor optical amplifier has an active region that is bandgap shifted to move its gain peak towards the emission wavelength of the laser diode, thus reducing its linewidth enhancement factor. The diode laser is preferably either a gain-coupled or index-coupled distributed feedback laser. The bandgap shift can be effected by known bandgap shifting methods, such as ion implantation, dielectric cap disordering, and laser induced disordering.

Abstract: A photonic integrated device having a substrate layer, epitaxial layers formed on said substrate layer and a guiding layer formed by one of the epitaxial layers. An optical waveguide is formed within the guiding layer. In the waveguide are a splitter (4) having at least two outputs, each output being transmitted to a Mach-Zehnder modulator (6, 8), the phase of the output of at least one modulator being shiftable, the signals being recombined to provide an optical phase shift key (PSK) output (14) wherein a trench is etched into the substrate layer between each pair of modulators to isolate the modulators from one another.

Abstract: A device comprises a tapered semiconductor optical waveguide which tapers, at an angle of taper with respect to a longitudinal axis of the waveguide, from a relatively wide region to a relatively narrow region, wherein the angle of taper varies along the length of the tapered waveguide such that at all points along the taper it is no greater than, and within a substantially constant angular separation of, the adiabatic limit of the fundamental mode of the waveguide at that point along the taper.

Abstract: A remote device such as a control value (4) is powered and controlled by optical energy, supplied by an intensity-modulated light source (8) and optical fiber (10). After conversion into electrical form, the light is detected at (12) and applied to a piezoelectric transformer (14). The output of the transformer powers and control an actuator (16) of the control value.

Abstract: The device includes an oscillator (1) to generate an electrical signal of a predetermined frequency and a signal divider (2) to split the electrical signal into first and second signals. The frequency of the second signal is tripled by tripler (3) and the tripled second signal is recombined with the first signal at signal adder (9) to produce a combined electrical signal. This combined electrical signal drives a Mach-Zehnder modulator (10).

Abstract: Increasing the gain-coupling of a DFB directly modulated semiconductor laser permits the output response to be overdamped without lowering the relaxation oscillation frequency of the output. The overdamping permits the laser to operate at modulation frequencies which approach the relaxation oscillation frequency with satisfactory error performance. The performance improvement is sufficient to permit operation of the laser in an uncooled environment.