Abstract: A method is provided for making cryogenic capacitance-voltage (C-V) measurements of semiconductor epitaxial layers without the need for measuring fully processed devices. The method utilizes impurity hopping conduction to obtain a compensator concentration profile. In a preferred embodiment, a metal electrode is evaporated onto the bottom of the substrate of a semiconductor wafer having a heavily doped substrate, a heavily doped epitaxial layer, and an undoped epitaxial layer. A mask is used to form metal electrode capacitor dots on the top of the undoped layer. The cryogenic C-V measurement system comprises a Helitran dewar with a wafer holder and electrical connections, a temperature controller, measurement electronics, and a microcomputer. A programmable dc source is stepped and combined with an ac voltage supplied by a lock-in amplifier. A preamplifier converts the current from a capacitor electrode on the wafer to a voltage measured by a lock-in amplifier.

Abstract: A method is provided for monitoring the refractive index of an optical film as it is being deposited on a substrate. The film is illuminated by a source of light at a wavelength that is outside and less than the reflectance band of the coating. If the refractive index of the film is initially matched to the refractive index of the substrate and has no abrupt changes in its gradient-index profile, reflectance from the surface of the film can be detected and measured. In the absence of interference fringing from internal reflections, surface reflectance of the interface of the film with the surrounding air or vacuum is closely related to the refractive index of the film at its surface. Thus, surface reflection is monitored to provide a control signal to the deposition apparatus to conform the refractive index of material being deposited to a predetermined refractive index profile specified for the desired optical film.

Abstract: An impurity band conduction (IBC) detector having a substrate and a thin layer IR active region is provided with a beveled edge for increasing the quantum efficiency of the detector. The edge of the transparent detector substrate is beveled at an angle equal to or greater than the critical angle for total internal reflection of radiation in the material of the substrate and active region of the detector. The radiation is directed into the detector normal or nearly normal to the beveled edge. The radiation travels the length of the detector due to total internal reflection within the detector. As a result, the radiation passes through the IR active region of the detector a plurality of times, thereby increasing the probability that a photon will be absorbed by an impurity within the IR active region and sensed by the detector.

Abstract: A digital mixer employs a plurality of flip-flops to mix two digital input signals and provide a beat frequency output. The first input signal is provided as a clock signal to a first D flip-flop and to a third JK flip-flop. The second input signal is provided as a clock signal to a second D flip-flop. The inverted output of the first flip-flop is provided as a clock input to a fourth JK flip-flop. The non-inverted and inverted outputs of the second flip-flop are connected, respectively, to the J and K inputs of the third flip-flop. The non-inverted outputs of the second and third flip-flops are input to a first AND gate, the output of which connects to the J input of the fourth flip-flop. Likewise, the inverted outputs of the second and third flip-flops are input to a second AND gate, the output of which connects to the K input of the fourth flip-flop. The non-inverted output of the fourth flip-flop provides a beat frequency that is one-half the difference frequency of the two input signals.

Abstract: Nonlinear optical techniques are utilized to provide an adaptive notch filter for removing narrowband noise from broadband RF communication signals. The received RF signal is converted to a corresponding acoustic wave propagated in an acousto-optic cell. Two mutually coherent beams of light are passed through and diffracted by the acousto-optic cell. The diffracted beams are modulated by the acoustic wave, the second beam being modulated at a predetermined time delay with respect to the first beam. By proper selection of the time delay, the narrowband components of the two beams remain mutually coherent while the broadband components become mutually incoherent. The two diffracted beams are then mixed within a photorefractive crystal so that a first mixed beam comprises substantially all of the narrowband components while a second mixed beam consists essentially of only the broadband components.

Abstract: A rotating cylindrical target surface is provided for the laser ablation process of depositing thin films on a substrate. The target is mounted in a vacuum chamber so that it may be rotated about the longitudinal axis of the cylindrical surface target and simultaneously translated along the longitudinal axis. A laser beam is focused by a cylindrical lens onto the target surface along a line that is at an angle with respect to the longitudinal axis to spread the plume of ablated material over a greater radial arc. The plume may be spread in the longitudinal direction by providing a concave or convex lateral target surface. The angle of incidence of the focused laser beam may be other than normal to the target surface to provide a more glancing geometry. Simultaneous roation about and translation along the longitudinal axis produce a smooth and even ablation of the entire cylindrical target surface and a steady evaporation plume.

Abstract: A process is described for growing at least one layer doped with a transition element of cobalt on a substrate by introducing a source of indium, such as tri ethyl indium, (C.sub.2 H.sub.5).sub.3 In or, a source of a group V element, a source of the transition element, such as cobalt nitrosyl tricarbonyl CO(NO)(CO).sub.3, and a source of phosphorus, to the substrate heated in an inert or reducing atmosphere at a pressure substantially between 1/100 atmosphere and one atmosphere to grow at least one semi-insulating semiconductor layer on the substrate.

Abstract: An optical crosspoint switch module is provided for a matrix of optical sources and receivers. The switch module includes a thin film waveguide atop a substrate, an array of input optical fibers aligned along one edge of the thin film waveguide, and a similar array of output fibers aligned along a second edge of the waveguide. The waveguide and/or the substrate comprise nonlinear optical material. A film containing a grating pattern to be written into the nonlinear medium as persistent but erasable holograms is placed above the waveguide. A spatial light modulator (SLM) is positioned above the patterned film and illuminated from above by either coherent or incoherent light. The SLM functions as a selective mask so that the grating pattern of the film can be written as holograms in selected areas of the nonlinear medium. The holograms written into the nonlinear medium diffract beams from the input fibers along the first edge of the waveguide to the output fibers along the second edge of the waveguide.

Abstract: Nonlinear optical devices and techniques are used to provide heterodyne detection for coherent optical communications. Heterodyne detection is achieved by matching the wave front of a local oscillator beam with the wave front of a received optical signal. Precise wave front matching provides high heterodyne efficiency and a wide field of view. In one embodiment, the received signal and a reference beam of the same frequency are directed into a nonlinear medium to form a volume hologram that contains the spatial information of the received signal. The reference beam is alternated with a local oscillator beam that has the same wave front and is parallel to the reference beam but at a different frequency. The hologram matches the wave fronts of the signal beam and the local oscillator beam to produce a large heterodyne signal. In an alternative embodiment, the received signal beam and the local oscillator beam are directed into a mutually pumped phase conjugator (MPPC).

Abstract: A monitor is provided for measuring and controlling the strain rate of a blank during forming. A light source directs light against the blank and a video camera is positioned and focused to view the light reflected from the blank while it is being formed. A video monitor and an image processor receive the signal from the camera. This signal is used to determine the strain rate based upon the dimensional change in reference marks on the blank. The image processor provides an output signal which can be used to control the strain rate in accordance with a predetermined strain rate profile for the particular part being formed.

Abstract: An impurity band conduction (IBC) infrared detector is provided with a photoluminescent (PL) layer proximate the blocking layer of the device. The PL layer comprises a narrow band-gap semiconductor material selected for generating long wavelength infrared (LWIR) photoluminescent photons in response to incident photons of selected spectra. The PL layer improves the quantum efficiency of IBC devices in detecting incident photons in the short wavelength infrared (SWIR), ultraviolet (UV), and X-ray spectra. The thickness of the PL layer can be varied to optimize the photoluminescent response to incident photons of a selected spectrum. In a back-illuminated detector array, absorption of a SWIR photon in the PL layer results in one or more LWIR photons emitted in a time that is sufficiently shorter than the multiplexer frame time.

Abstract: A method is provided for monitoring and controlling the deposition of an optical thin film having a refractive index gradient. The optical material to be deposited is evaporated at a controllable rate. In a coevaporation process, evaporation of material having a lower index of refraction is generally held at a predetermined rate while evaporation of material having a higher index of refraction is controllable. During deposition, the film and substrate are illuminated by a broadband light source. The incident light reflected by the film and substrate produces an interference pattern comprising a reflectance spectrum that is detected to compute an optical thickness estimate of the film. The detected reflectance is compared to a reflectance specified for that optical thickness by a predetermined refractive index profile of the desired film. The controllable rate of evaporation is then adjusted so that the refractive index of the material being deposited conforms to the predetermined profile.

Abstract: A method for planarizing surfaces in multi-layered semiconductor structures using elevated features in the form of semiconductor materials, such as for forming heterojunctions, or interconnection metal. A process of forming the features includes leaving residual photoresist on the features. After feature formation and definition of transistor or other structure locations, dielectric material is deposited across the structure. Remaining photoresist is subsequently removed along with dielectric deposited thereon leaving dielectric between the features. A layer of polyimide is spun on the structure and into depressions between the dielectric and features. Typically material deposition, etching, dielectric backfilling and spin-coating steps are repeated until a predetermined number of contact or conductivity regions or interconnection metal layers are formed in the desired multi-layered structure.

Abstract: A mutually pumped phase conjugator (MPPC) is used to remove spatial distortions from a high power laser beam. The high power beam with its "dirty" spatial profile is directed into one side of the MPPC. A spatially clean beam at the same nominal frequency as the high power beam is output from a continuous wave (CW) laser and directed into the opposite side of the MPPC. As a result of mutually pumped phase conjugation, the MPPC returns a phase conjugate beam that retains the clean spatial profile of the CW beam but acquires the temporal characteristics of the high power beam. A Faraday isolation system may be used to separate the phase conjugate beam from the incident CW beam to provide an output beam having a clean spatial profile. If desired, the high power beam can be transformed into an image bearing output beam simply by modifying the incident CW beam with a transparency or spatial light modulator.

Abstract: A non-uniform heating system is provided for liquid crystal displays. The system includes structure for applying a greater concentration of heat to the periphery of LCDs. Because mounting structures produce large heat sinks around the edges of LCDs, providing greater heat to the edges results in a more uniform distribution of heat across the LCDs. In another aspect of the heating system, rapid warming may be provided for preselected critical areas of a display to reduce warm-up time, reduce power consumption, and provide mission critical displays in situations such as scrambles of military aircraft on cold weather alert.

Abstract: A compact backlighting luminaire is provided for liquid crystal displays (LCDs). The body of the luminaire is formed of optically clear glass or acrylic resins. The body comprises a mesa extending from a base comprising a flange extending around the periphery of the mesa. The top of the mesa comprises at least two non-parallel sloped surfaces. The base of the luminaire body may form a wedge with the flange being thicker at one edge than at an opposite edge. The bottom surface and edges of the body may be coated with a reflective film. A fluorescent lamp extends around the periphery of the mesa and is supported by the flange. A cover may be provided to extend over the mesa and around the periphery of the flange to secure the lamp, to reduce illumination losses, and to provide a mounting surface for an LCD.

Abstract: An optical beamforming network is provided for controlling the RF radiation pattern of a phased array antenna. Light from a first laser is modulated by a spatial light modulator that is user-programmed with the desired far field radiation footprint. The modulated light beam is directed through a Fourier transform lens and onto a beam splitter where it is combined with light from a second laser that is frequency offset by the RF center frequency of the antenna. Light from the beam splitter is recovered by first and second fiber optic bundles. Each optical fiber leads to a corresponding photodetector that detects the beat frequency produced by the two frequency offset light beams. The outputs of corresponding photodetectors of the two fiber optic bundles are combined to control the radiation of a corresponding radiation element of the phased array. The use of two sets of optical fibers and photodetectors improves the signal-to-noise ratio of the system.

Abstract: An adaptive optical network is provided for the implementation of learning algorithms. The network comprises a double Mach-Zehnder interferometer in conjunction with a photorefractive crystal that functions as a holographic medium. Light from selectable sources on opposite sides of a beamsplitter is passed through the interferometer, at least one arm of which includes a spatial light modulator for imprinting a data pattern on the light. The light is directed into the holographic medium to develop a refractive index grating corresponding to the data pattern. Light from the hologram is sensed by a photodetector that provides a signal to a threshold device. The output of the threshold device is compared with a reference signal to produce an error signal that can be used to select the source of light directed through the network. The interconnections of the optical devices function to compute the inner product between the elements of the data pattern and their weight factors.

Abstract: Methods for reducing linewidths of Field Effect Transistors (FETs) and making FETs with 0.5 to 0.15 .mu.m effective gate lengths are used separately or in a combined process sequence, that combines enhancement/depletion mode and microwave Metal-Semiconductors FETs (MESFETs) on the same GaAs chip. Photoresist linewidths are used to form dummy or substitutional gates using optical lithography with no deliberate overexposures. The dummy gate may be used as a mask for N+ implantation. The photoresist linewidth is then reduced in its lateral basewidth while preserving its height to basewidth aspect ratio in an isotropic oxygen plasma etch. A nonconformal dielectric film of silicon monoxide is deposited over the photoresist linewidth patterns. Dielectric reverse liftoff of the SiO pattern transfer dielectric provides a self-aligned stencil mask with respect to the N+/N- interfaces. The SiO stencil is also a dielectric spacer with respect to the N+/N- interfaces.

Abstract: A data storage device includes two registers associated with each cell of the memory. The first register forms a read/write memory register, and the second register forms a write-only shadow register connected to the memory register. During normal operations, each memory register operates as an independent random access memory (RAM) cell and each shadow register operates as an independent write-only RAM cell. When data is written to a shadow register, a flag bit is set. Subsequently, a validity check may be performed to verify the data. If the data does not verify, a clear line may be used to clear the flag bits. If the data verifies, the data in each shadow register with a flag bit set can be loaded into its corresponding memory register in a gang loading operation. If a shadow register flag bit is not set, the data in its corresponding memory register is not changed during gang loading.