Bookham Technology Limited

Plessey Overseas Limited

Gec-marconi Limited

Oclaro Technology Limited

Robert Graham Walker

Robert Anthony Griffin

Robert Ian Johnstone

Andrew John Ward

Andrew Cannon Carter

Kelvin Prosyk

Douglas Charles John Reid

David James Robbins

Guy Towlson

The present invention concerns tunable distributed Bragg reflector (DBR) semiconductor lasers, in particular a DBR laser with a branched optical waveguidewithin which a plurality of differently shaped lasing cavities may be formed, and a method of operation of such a laser. The laser may comprise a phase control section (), gain section (), a sampled grating DBR () giving a comb-line spectrum and two tunable, chirped DBRs () for broadband frequency training and a coupling section ().

Tunable laser

An improved method is provided for fabricating a polarisation rotator in a rib waveguide having a propagation axis and opposite side walls. The method includes etching a pit in the substrate surface to form a recess in one of the side walls of the waveguide, during formation of the waveguide on the substrate surface, so as to provide an asymmetric waveguide section for imparting polarisation rotation to radiation propagated along the propagation axis. Preferably the pit is formed by a wet etching step forming an upper side surface within the recess that is inclined relative the waveguide side walls, and the waveguide side walls are formed by a dry etching step to extend perpendicularly to the substrate surface. In addition the dry etching step forms a lower side surface adjoining the upper side surface within the recess and tilted relative to the upper side surface. Such a method is significantly simplified as compared with prior art production methods, as well as providing greater yield and more predictable device performance since mask alignment errors no longer affect the design parameters of the rotator.

Polarization rotators

An optical device comprises a semiconductor structure including first and second ridge waveguides, each waveguide comprising a ridge extending across a surface of the semiconductor structure. The ridge of the first waveguide has a first height above a first region of the surface, and the ridge of the second waveguide has a second, greater, height above a second region of the surface. The semiconductor structure includes a multimode interference (MMI) region situated between the first and second ridge waveguides, which provides a transition between them. At least a part of the MMI region is tapered in width and/or at least a part of the first and/or second ridge waveguide is tapered in width in a direction extending away from the MMI region.

Semiconductor optical device

The invention concerns a guided wave spatial filter () for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections (LL) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter () is implemented using rib waveguides () for the sections with associated relatively deeply and relatively shallowly etched structures () for imparting to the sections their radiation mode filtration characteristics. The spatial filter according to the invention can be incorporated into optical splitters and optical modulators to enhance their performance and desensitise them to higher-order mode radiation injected thereinto.

Guided wave spatial filter

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.

Optical modulators operated in parallel push-pull mode

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 () having at least two outputs, each output being transmitted to a Mach-Zehnder modulator (), 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 () wherein a trench is etched into the substrate layer between each pair of modulators to isolate the modulators from one another.

Photonic integrated device

An integrated optical device including a direction coupler between first and second waveguides whereby to transfer light energy between the first and second waveguides, the directional coupler including a first region in which the first and second waveguides converge towards one another while the electromagnetic field regions associated with the waveguides interact, and a second region in which the first and second waveguides are merged into a single waveguide structure having at least twice the width of the first or second waveguide, the first and second regions being dimensioned to control or eliminate the dependence of the directional coupler upon polarization of light in the waveguides.

Integrated optical device with zero-gap and well-spaced regions

A guided-wave optical wavelength duplexer fabricated as an integrated optical device, comprising input ports (2, 4) for light at different wavelengths (a.sub.1, a.sub.2) coupled to first and second waveguides (6, 8) formed on a substrate surface, the first and second waveguides having first and second coupler regions (10, 12) to enable light to be transferred from one waveguide to the other, the first and second waveguides as at (26) between the first and second coupler regions being formed as circular arcs having the same center to provide an accurately defined optical path length difference, so that light at a first wavelength (a.sub.1) is output through one output port (14) and the second component (a.sub.2) is output through another output port (16).

Growing community of inventors

Northampton, United Kingdom

Robert Graham Walker