Abstract: A planar integrated circuit includes a semiconductor substrate having a substrate surface and a trench in the substrate, a waveguide medium in the trench having a top surface and a light propagation axis, the trench having a sufficient depth for the waveguide medium to be at or below said substrate surface, and at least one Schottky barrier electrode formed on the top surface of said waveguide medium and defining a Schottky barrier detector consisting of the electrode and the portion of the waveguide medium underlying the Schottky barrier electrode, at least the underlying portion of the waveguide medium being a semiconductor and defining an electrode-semiconductor interface parallel to the light propagation axis so that light of a predetermined wavelength from said waveguide medium propagates along the interface as a plasmon-polariton wave.

Abstract: An optical circuit including a semiconductor substrate; an optical waveguide formed in or on the substrate; and an optical detector formed in or on the semiconductor substrate, wherein the optical detector is aligned with the optical waveguide so as to receive an optical signal from the optical waveguide during operation, and wherein the optical detector has: a first electrode; a second electrode; and an intermediate layer between the first and second electrodes, the intermediate layer being made of a semiconductor material characterized by a conduction band, a valence band, and deep level energy states introduced between the conduction and valence bands.

Abstract: An optical modulator is constituted by a planar lightwave circuit incorporating a silicon waveguide (2) provided on a silica substrate (1). The silicon waveguide has a resonant cavity (5) formed therein. The resonant cavity (5) may conveniently be implemented as a periodic array of holes defining a photonic bandgap device. The waveguide may be a photonic crystal waveguide. An electric field is applied to the resonant cavity (5) in order to alter the Q-factor, and hence the transmission properties, thereof, either via the MOS effect or via alteration of the width of the depletion region of a p-n junction. A control unit (10) controls the voltage that is applied to the resonant cavity (5). and thus controls the modulation of light at the resonant frequency/frequencies of the cavity (5).

Abstract: A strained layer superlattice comprising Ge.sub.x Si.sub.1-x layers interleaved with Si layers is an excellent photodetector at infrared wavelengths due to the large shift in bandgap caused by the strain in the superlattice.

Abstract: Disclosed is a novel switching device. In its currently preferred embodiment the device comprises a conductive path that comprises a superconductive section, with the remainder of the path being non-superconductive, means for applying a voltage across the path such that a current flows, and means for changing the current in the path from a first value to a second value, where one of the two values is below, and the other is above, a critical current associated with the superconductive section of the path. Depending on the choice of applied voltage and path parameters changing the current from the first to the second state results in switching of the current, either oscillating between two levels of current, or to a steady value. Exemplarily, the current is changed by changing the applied voltage or by changing the resistance of the non-superconductive portion of the conductive path. The device can be used as, for instance, a microwave oscillator or a (binary) photodetector.

Abstract: A photodetector, comprising a Ge.sub.x Si.sub.1-x superlattice region between two silicon cladding layers in which the Ge.sub.x Si.sub.1-x layers absorb light, is described.

Abstract: A multi-quantum well laser having a Ga.sub.0.47 In.sub.0.53 As/Al.sub.0.48 In.sub.0.52 As active region emitting at 1.55 .mu.m and well layers having a thickness less than 150 Angstroms.

Abstract: In an avalanche diode of gallium arsenide, e.g. an IMPATT diode, the optimization of the coefficient of ionization by impact in the case of impacts initiated by holes when the electrical field propels the carriers along the axis of 1 1 1 of the monocrystal, has been utilized. The structure comprises a substrate of Ga As with two large faces perpendicular to the axis 1 1 1 and layers obtained by epitaxial growth from one of these large faces. Arrangements are made to ensure that the electrical field is as parallel as possible to this crystalline axis. The improvement in efficiency is of the order of 20%.