Abstract: A planar silicon dioxide waveguide with low loss for the TE mode has been built on a silicon wafer by separating the waveguide from the substrate with a relatively thin layer of polycrystalline silicon and a layer of silicon dioxide having a combined thickness less than that of the waveguide. The separating layers provide a high antiresonant reflectivity which is operative over a broad range of wavelengths.

Abstract: An access port assembly (10) for a main lightwave transmission fiber (16) is made by machining a notch (26) into it by carbon dioxide laser nibbling to form notch faces (28, 30) which extend into the core region (18). The end face (32) of a second, receiving fiber (12) is placed in contact with the notch faces (28) to optically couple it to the core (18) of the main fiber (16). An optical epoxy cement (34) holds the two members in position and matches and index of refraction. A third, transmitting fiber (14) is similarly connected to the main fiber (16) in a second notch and is perpendicular to the receiving fiber (12).

Abstract: An electrooptic polarization multiplexer/demultiplexer incorporates an electrooptic, directional coupler switch structure. The multiplexer/demultiplexer includes a substrate of birefringent, electrooptic material, a pair of phase matched, dielectric waveguides embedded in the substrate and spaced closely together over a distance L (the coupler or device length), a buffer layer of insulating material positioned over the substrate and the pair of electrodes, and a plurality of metallic electrodes positioned on the buffer layer in the vicinity of the waveguides. Electrodes are arranged in a multi-section, reversed .DELTA..beta. configuration. The distance L is selected such that 1.ltoreq.L/1.sub.TE .ltoreq.2 and L/1.sub.TM .ltoreq.0.5, where 1.sub.TE and 1.sub.TM are transfer lengths for the TE and TM modes, respectively.

Abstract: A fused silica glass optical fiber 10 is machined by a pulsed infrared laser beam 20 from a carbon dioxide laser 22 focussed by a germanium lens 24. The beam has a power density of about 70,000 watts per square centimeter at the focussed machining region b and is pulsed at about one pulse per second with a one-half second pulse duration. The fiber workpiece edge is gradually brought into the beam from the side to result in progressive flash evaporation.

Abstract: An MOS current steering circuit (10) includes a current mirror arrangement with an input branch (12) and an output branch (16). In the input branch, the conduction channels of a current-limiting transistor (M1) and a current mirror input transistor (M3) are connected in series with each other between a first power supply voltage node V+ and one side of a current source (14). The other side of the current source and the gate of the current-limiting transistor are connected to another supply voltage node (V-). In the output branch, a current mirror output transistor (M4) has one side of its conduction channel connected as a current output node (D). The gates of the input and output transistors are connected together and to the common node (A) of the input transistor and the current source. A control transistor (M2) has its conduction channel connected between the other side of the output transistor and the first voltage supply node.

Abstract: A modular, hierarchical local area network is realizable by using existing twisted pair wiring, for example, in a building together with several elements known as network access units and hub units. A network access unit is connected to a device (microprocessor, display terminal, peripheral device, other local area network, information systems network or the like) in the local area network to give that device access to and from the network. The network access device is designed for simple daisy chaining with other devices to form a node when devices are colocated in the same section or room in the building. The hub unit is the network building block which permits extensive expansion of the local area network. It provides a connection point for access units or other hub units, performs collision detection operations, if necessary, and serves as a loop-back point for the network.

Abstract: Optical functions such as Q-switching, mode locking, cavity dumping, and modulation are generated by a simple laser arrangement which includes a gain medium and an electrically controllable, optical waveguide device optically coupled to the gain medium. The gain medium and waveguide device are either interposed between two reflective surfaces or coupled by a waveguide in order to form a single composite cavity laser structure.

Abstract: High speed, high quantum efficiency, low dark current, and avalanche gain greater than 10 are exhibited by a long wavelength avalanche photodetector including in succession a terminal region of p-type indium phosphide (InP) a multiplication region comprising first and second layers of n-type indium phosphide (InP), a grading layer of n-type indium gallium arsenide phosphide (InGaAsP), and an absorption region of n-type indium gallium arsenide (InGaAs).

Abstract: The invention is a nonlinear or bistable optical device having a low switching energy. The invention uses a means responsive to light for generating a photocurrent, a structure having a semiconductor quantum well region, and means responsive to the photocurrent for electrically controlling an optical absorption of the semiconductor quantum well region. The optical absorption of the semiconductor quantum well region varies in response to variations in the photocurrent. A photodiode or phototransistor may be used as the means responsive to light, and may be made integral with the structure having the semiconductor quantum well region. An array of devices may be fabricated on a single chip for parallel logic processing.

Abstract: In a metal-oxide-semiconductor device process, parasitic capacitance is significantly reduced by differentially oxidizing a substrate and a gate mesa thereon prior to ion implantation and "drive-in" of the drain and source regions. This results in a channel region being formed in the substrate beneath and substantially coextensive with the gate mesa. The conductivity of the channel region is different from the conductivity of the adjacent source and drain regions. In one embodiment, the source and drain regions each extend to a greater depth into the substrate with increasing distance from the channel region.

Abstract: A four-wave mixer which uses a multiple quantum well structure as a nonlinear optical material is provided. There are provided means for providing a first beam of light which propagates through said multiple quantum well structure, and means for providing a second beam of light which also propagates through said multiple quantum well structure and substantially overlaps said first beam of light within said MQW structure. At least one ouput phase conjugate beam of light is produced by interaction of said first and said second beams of light with said multiple quantum well structure. An alternate embodiment has two counterpropagating pump beams and a probe beam of light which produce a backward scattered phase conjugate beam of light.

Abstract: Single longitudinal mode operation is achieved and maintained under CW and high speed (Gbps) current modulation conditions by a short coupled cavity laser including a short cavity semiconductor laser having two parallel mirror facets and a reflective surface spaced apart from and in predetermined relationship with one of the mirror facets. A short external cavity resonator is formed between the one mirror facet and the reflective surface. In general, the laser cavity length is related to the external cavity resonator length by the equation, nL=md, where nL is the effective optical length of the injection laser, d is the length of the external cavity resonator, and m is a positive number preferably between 2 and 10.

Abstract: A semiconductor apparatus is provided. The apparatus has a multiple layer heterostructure having first and second material layers having first and second bandgaps, respectively and a semiconductor layer of a third bandgap being fabricated between said material layers, the bottom of the conduction band of said semiconductor layer is below the bottom of the conduction band of said material layers, and the top of the valence band of said semiconductor layer is above the top of the valence band of said material layers, the thickness of said semiconductor layer is chosen sufficient for carrier confinement effects within said semiconductor layer to influence the optical properties of said multiple layer heterostructure, and means for applying an electric field to the multiple layer heterostructure in order to vary an optical absorption coefficient and an index of refraction of the multiple layer heterostructure in response to the electric field.

Abstract: A method of etching a semiconductor crystal is given. The crystal includes elements selected from one of the groups: (a) indium and phosphorus; (b) gallium and arsenic; (c) aluminum and arsenic. The method comprises the steps of placing the crystal in an aqueous solution of H.sub.3 PO.sub.4 or HCl, and while the crystal is in contact with the solution illuminating predetermined regions of the crystal with light so that etching proceeds at the illuminated predetermined regions much more rapidly than at nonilluminated regions of the crystal. The method also includes focusing the light to a small spot on the crystal and moving the spot on the crystal so that a groove is etched in the crystal.

Abstract: Store group circuits (102a,b,c or 202a,b,c) in fixed priority bus allocation arrangements eliminate lockouts and reduce delays for devices (101a,b,c) requesting access to a shared resource such as a data bus. The store group circuit stores (111 or 205-1 through 205-3) all access requests (REQA, REQB, REQC) from the devices present at a time instant, inhibits (110 or 210) storage of subsequent requests until each device associated with a stored request is granted access (GRANTA, GRANTB, GRANTC), and removes from storage each request associated with a device which has been granted access. Arbitration is performed among the stored requests using existing arbiters (103) in the fixed priority bus allocation arrangement. Bus access is guaranteed for devices whose requests are stored in the store group circuit thereby eliminating lockouts.

Abstract: A substrate heating arrangement suitable for use in ultra-high vacuum MBE includes a filament responsive to a DC current for generating thermal energy, a metallic enclosure surrounding the filament and having an aperture at one end thereof, an intermediate semiconductor substrate parallel to and separated from a semiconductor growth substrate, and a substrate support mounted to the enclosure capable of holding the substrates in the prescribed relationship.The intermediate semiconductor substrate regulates the temperature on the surface of the semiconductor growth substrate to be less than or equal to a fixed temperature (approximately 1100.degree. C. for silicon) regardless of the DC current applied to the filament.

Abstract: In a digital, time division multiplex communication system, a first-in, first-out buffer (10) at each subscriber station is employed to establish a conference call. The digital words of the conferees being listened to are entered into the buffer as they are received. They are then read out at a different bit rate such that they all occupy an equal fraction of the word period. The words are decoded in a standard D/A converter (11) and combined in a filter (12).

Abstract: A row and column matrix of strip electrodes is utilized for switching bistable liquid crystal display cells from the vertical state to the horizontal state via resistive heating by applying an electric current of sufficient magnitude and duration to selected electrodes. Resistive heating causes the liquid crystal to undergo a phase transition from the nematic mesophase to an isotropic phase. Extinction of the current permits the liquid crystal to cool preferentially into the horizontal state of the nematic mesophase. Horizontal-to-vertical state switching is performed by conventional electric field effect techniques.

Abstract: In stream cipher operation (FIG. 1), a public key cryptographic system employs a filter (21, 22, 31, 32, 33) to alter each sequence (S.sub.i) input to the encryption devices (FIGS. 2 and 3) at the transmitter and the receiver of the system. Characteristics of the filter are known only to the sender and authorized receivers.

Abstract: A plurality of pairs of layers comprising gold and zinc are successively evaporated onto a p-type Group III-V semiconductor material such as indium phosphide. A final layer of gold is evaporated onto the pairs of layers prior to heating the multilayer contact. Successive layers of chromium and gold may be evaporated onto the final gold layer prior to the annealing step.