Abstract: Disclosed herein is a semiconductor device comprising: a silicon substrate; a germanium layer; and a buffer layer comprised of at least one layer of III-V compound, formed directly on silicon; at least one layer containing III-V compound quantum dots wherein one or more facets are formed using focused ion beam etching such that the angle between the plane of the facet is normal to the plane of growth.

Abstract: A semiconductor device comprising a nominally or exactly or equivalent orientation silicon substrate on which is grown directly a <100 nm thick nucleation layer (NL) of a III-V compound semiconductor, other than GaP, followed by a buffer layer of the same compound, formed directly on the NL, optionally followed by further III-V semiconductor layers, followed by at least one layer containing III-V compound semiconductor quantum dots, optionally followed by further III-V semiconductor layers. The NL reduces the formation and propagation of defects from the interface with the silicon, and the resilience of quantum dot structures to dislocations enables lasers and other semiconductor devices of improved performance to be realized by direct epitaxy on nominally or exactly or equivalent orientation silicon.

Abstract: Disclosed herein is a semiconductor device comprising: a silicon substrate; a germanium layer; and a buffer layer comprised of at least one layer of III-V compound, formed directly on silicon; at least one layer containing III-V compound quantum dots wherein one or more facets are formed using focused ion beam etching such that the angle between the plane of the facet is normal to the plane of growth.

Abstract: A semiconductor device comprising a nominally or exactly or equivalent orientation silicon substrate on which is grown directly a <100 nm thick nucleation layer (NL) of a III-V compound semiconductor, other than GaP, followed by a buffer layer of the same compound, formed directly on the NL, optionally followed by further III-V semiconductor layers, followed by at least one layer containing III-V compound semiconductor quantum dots, optionally followed by further III-V semiconductor layers. The NL reduces the formation and propagation of defects from the interface with the silicon, and the resilience of quantum dot structures to dislocations enables lasers and other semiconductor devices of improved performance to be realized by direct epitaxy on nominally or exactly or equivalent orientation silicon.

Abstract: A method of manufacturing a semiconductor device suitable for optoelectronic switching in response to light of wavelengths in the range 1200 nm to 1600 nm, comprising forming an undoped InGaAs layer on an insulative semiconductor substrate and bonded on opposed sides to a pair of electrical contact layers adapted to constitute the electrodes of a switch, comprising forming the bulk point defects by irradiating the InGaAs layer with Nitrogen ions.

Abstract: This invention describes a technique and apparatus to use any tuneable laser to generate a specified output frequency without controlling its temperature. This technique only involves a thermal sensor and a controller a determine the current(s) of voltage(s) applied to the grating or tuning section(s) to obtain the required wavelength. The control loop can be implemented using a programmed microprocessor, an amplifier and a low pass filter.

Abstract: A method of transmission of radio signals over all types of graded-index multimode fibre is provided. The method comprises launching optical radiation into the core of the multimode fibre away from the centre of the core so as to strongly excite a subset of the available modes of the multimode fibre. The subset of modes excited are within a small number of mode groups and thus have similar propagation constants leading to a reduction in modal dispersion and modal interference and smoothing of the frequency response passband region beyond the fibres specified 3 dB base band bandwidth assisting RF transmission and recovery from this region.

Abstract: A method is provided for the transmission of digital and radio frequency signals, for example for multiservice applications, over all types of multimode optical fibre link using laser diodes. The method comprises launching optical radiation into the core of the multimode optical fibre, in a manner that restricts the number of excited modes within it. The subset of modes that are excited suppress additional noise due to the presence of a multiplicity of signals, and ensure high quality transmission.

Abstract: This invention describes a technique and apparatus to use any tuneable laser to generate a specified output frequency without controlling its temperature. This technique only involves a thermal sensor and a controller to determine the current(s) or voltage(s) applied to the grating or tuning section(s) to obtain the required wavelength. The control loop can be implemented using a programmed microprocessor, an amplifier and a low pass filter.

Abstract: Laser frequency locking apparatus (5), comprising: a slave laser (15), having associated with it means (14, 18) for coupling and/or means (18, 25) for coupling and propagating signals received and emitted; a phase lock loop (24); and a controller (16), operable to control the slave laser, wherein an output of a reference signal source (1) associated with a master source (2, 3), and receivable therefrom, is utilised in the phase lock loop to render the output frequency of the slave laser the same as an output frequency of the master source. The invention described relates to a technique for generating a set of highly stable optical frequency channels. There are provided methods and systems of locking laser frequencies and of synthesizing frequencies.