U.S. Philips Corporation

Jean-Bernard Theeten

Marko Erman

Nakita Vodjdani

Serge Gourrier

Philippe Autier

Martine Naillon

Jean Marc Auger

Method of and arrangement for image data compression by vector quantization in accordance with a precoding in blocks, thereafter comparing by means of a neural network precoded blocks with reference words stored in the form of a code book so as to transmit selected indices to a receiver. In accordance with the method, the neural network effects a learning phase with prescribed prototypes, thereafter with the aid of test vectors originating from the image generates an adaptive code book which is transmitted to the receiver. This adaptation utilizes attractors, which may be induced metastable states, of the neural network, and which are submitted to an optimizing procedure. The arrangement can process images with a view to their storage. It is also possible to utilize two devices which operate alternately, one device for generating the adaptive code book and the other one to utilize it with the object of processing television pictures in real time.

Method of and arrangement for image data compression by means of a

A method of manufacturing semiconductor devices is set forth using reactive ion plasma etching in which an optical grating is formed to etch underlying regions, such as dielectric material, semiconductor material, or alternate layers of different semiconductor material. The optical grating is formed with a rectangular profile having grooves and mask strips on a sample material where each of the grooves has a width L.sub.S substantially equal to the width L.sub.M of the mask strips. The optical grating is formed of a material which may be one of a photoresist, a dielectric compound, a metal, or a metallic compound. This method enables control of reactive ion etching during manufacture of integrated circuits of III-V compounds.

Method of manufacturing semiconductor devices

A separation structure for selecting the propagation mode of the light waves in a light wave guide, the latter being constituted by a strip (100) of a semiconductor material having a first refractive index formed on a semiconductor substrate (10) of a material having a second refractive index lower than the first index and such that the light is confined in the strip forming the guide. The structure is arranged in the path of the light beam in such a manner that it de-limits in the guide on the one hand at least one region (G.sub.1), in which the propagation of the light wave is monomode, and on the other hand a region (G.sub.11), in which the propagation is bimode. According to the invention the said separation structure is formed by an abrupt variation of the dimension of the guide perpendicular to the substrate, the flat surface of the substrate being chosen as reference for the measurement of this dimension in such a manner that, by defining e.sub.1 as the dimension of the guide perpendicular to the substrate in the monomode region and e.sub.2 as its dimension in the bimode region, these dimensions are associated by the relation ##EQU1## in which .lambda. is the transported wavelength, n.sub.g is the refractive index of the light wave guide (100) and n.sub.S is the refractive index of the substrate (10).

Separation structure, optical switching element including such

An optical switching element including two parallel light wave guides, whose opposite walls are mutually separated by a small distance (d), the so-called coupling distance, each constituted by a strip of a semiconductor material formed on a semiconductor substrate having a refractive index lower than that of the guides, these guides each transporting a monomode wave and the switching being initiated by the effect of polarization means applied to the guides, characterized in that the strip constituting one of the guides (G.sub.1) designated as first guide is formed as a first uniform layer on the substrate (1), in that the strip constituting this guide is covered by a uniform intermediate layer (I) of a compatible semiconductor material, having an index lower than that of the guides and having a thickness which forms the coupling distance between the two guides, in that the strip constituting the other guide (G.sub.2) designated as second guide is formed as another uniform layer at the surface of the intermediate layer, and in that by the effect of the polarization means applied to the guides the light which is introduced into one of the guides parallel to its optical axis at a first distance from the substrate is caused to propagate through the other guide parallel to the optical axis of the latter at a second distance from the substrate, the assembly of the first guide forming with the second guide and with the intermediate layer a so-called stracked structure, whose longitudinal dimension is the coupling length.

Optical switching element between two light wave guides and optical

A coupling member between an input light wave guide transporting a main light beam and secondary light wave guides each transporting a part of the intensity of the main light beam. The coupling member is monolithically integrated with the wave guides on a semiconductor substrate. The coupling member comprises a plate having parallel surfaces perpendicular to the plane of the substrate. The plate has a refractive index different from that of the main light wave guide. The parallel surfaces of the plate form interfaces separating the propagation medium of the wave guides (I, R, T) from the propagation medium constituted by the plate.

Optical wave guides and coupling member monolithically integrated on a

A semiconductor device comprises a wave guide which permits propagation of light in the range of wavelengths between 0.9 and 1.6 .mu.m. This wave guide is formed on a crystallographic oriented substrate of monocrystalline semiconductor material from the group III-V covered with a layer of a dielectric material. Grooves are etched in the dielectric material according to the configuration chosen for the wave guide, and correspondingly into the substrate. The wave guide is obtained by anisotropic epitaxial growth of the III-V semiconductor material from the substrate in these grooves, and is bounded on its lateral and upper parts by crystallographic faces having a specific orientation relative to the plane of the substrate surface. The attenuation obtained for such wave guides is of the order of 1 dB/cm for light having a wavelength of 1.06 .mu.m.

Semiconductor device comprising a light wave guide

A method of manufacturing a semiconductor device is provided in which a surface of a substrate containing gallium and arsenic is treated in a first plasma containing hydrogen, and then, is coated with a layer of silicon nitride in a second plasma containing silicon and nitrogen. According to the invention, arsenic is added to the first plasma in the form of arsine. Further, the substrate is heated to a temperature below 450.degree. C. during such treatment. After this treatment, but before the coating, the substrate is superficially converted into a surface layer of gallium and arsenic nitrides in a third plasma containing nitrogen. In this way, an almost ideal passivation of the surface of a gallium and arsenic containing substrate can be obtained.

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Ozoir-La-Ferriere, France

Jean-Bernard Theeten