Abstract: A flexible rejection filter removes coherent radiation from an incoming beam of light. The filter includes a beamsplitter for dividing the transmitted portion into first and second beams. A photorefractive crystal in the paths of the first and second beams couples coherent radiation from the first beam to the second beam. A focal plane detector follows the crystal in the path of the first beam for sensing the incoherent radiation in the first beam, while a beam dump follows the crystal in the path of the second beam for absorbing the coherent radiation of the second beam. Other filter configurations can utilize contradirectional energy coupling or resonator structures in conjunction with photorefractive media.

Abstract: A magnetic switch for recording the change in position of a magnetic field includes a first object on which is positioned a source of magnetic force for creating a magnetic field and a second object on which is positioned at least one type II superconducting medium. The type II superconducting medium exhibits a permanent magnetic component after exposure to a magnetic field, such that relative motion between the first object and the second object causes the magnetic field to induce a residual magnetization in the superconducting medium.

Abstract: An optical encoder for sensing angular position includes a rotatable optical medium having a major surface and an axis of rotation perpendicular to the surface, with a plurality of uniformly sized angular sectors defined on the surface. An annular absolute track is defined on the surface concentric with the axis, a plurality of digital bits being formed on the surface in sequence along the absolute track within each sector. Each such bit is optically readable as a binary 1 or a binary 0, with each plurality of bits defining a binary word. A first series of optically detectable incremental marks are evenly spaced around a first incremental track on the surface. The binary word in a sector is optically read to identify the angular position of that sector and indicate the approximate angular position of the medium, while the first series of incremental marks can be optically detected to refine the approximate angular position indication.

Abstract: A C-up HBT is made to operate in the microwave/millimeter frequency range by self-aligning the collector uprisers on the base relative to proton damaged emitter regions and the base contacts which minimizes carrier injection into the extrinsic base. The use of about 7-10% indium in the indium gallium arsenide base is sufficient to stop the FREON-12 etch at the base after totally etching through the collector and single self-aligning mask.

Abstract: A liquid crystal display includes a polarizer layer, an analyzer layer, a liquid crystal layer disposed between the polarizer layer and the analyzer layer, a first electrode proximate to a first major surface of the liquid crystal layer, and a second electrode proximate to a second major surface of the liquid crystal layer. The first and second electrodes are adapted to apply a voltage across the liquid crystal layer when the electrodes are connected to a source of electrical potential. A multilayer thin film compensator is disposed between the polarizer layer and the analyzer layer, the multilayer compensator including a first plurality of layers, each having a first refractive index and a first thickness, alternating with a second plurality of layers, each having a second refractive index and a second thickness.

Abstract: Heterojunction bipolar transistor is formed by using a common photoresist mask for self-aligning all critical dimensions including emitter and emitter contact to base contact to proton damaged collector regions beneath base contact and to passivate emitter periphery at same time.

Abstract: A polarization independent energy exchanger transfers optical energy from a first coherent beam of optical energy to a second coherent beam of optical energy where the second beam is coherent with respect to the first beam, the second beam is counterpropagating with respect to the first beam, and the second beam possesses substantially the same polarization as the first beam. The energy exchanger includes a nonlinear optical uniaxial crystal having electro-optic coefficients r.sub.13 and r.sub.23 of equal magnitude and having a sufficiently large photorefractive charge density to achieve efficient contradirectional two-beam coupling, independent of the polarization states of the first and second beams. The crystal is oriented to receive the first and second beams therein such that the optic axis of the crystal is aligned parallel to the propagation directions of the first and second beams.

Abstract: The multicolor focal plane array of this invention detects and distinguishes between incoming electromagnetic radiation within a first band of wavelengths and incoming electromagnetic radiation within a second band of wavelengths which includes the first wavelength band. The array includes a substrate and a two dimensional array of detectors disposed on the substrate and responsive to electromagnetic radiation within a predetermined range of wavelengths including the first and second wavelength bands. A first thin film filter is disposed on the substrate and interposed between the incoming radiation and a subset of the detectors in the array to prevent radiation outside of the first wavlength band from reaching the detectors. A second thin film filter is disposed on the substrate and interposed between the incoming radiation and all of the detectors in the array to prevent radiation outside of the second wavelength band from reaching the detectors in the subset.

Abstract: A mask and lithographic process is disclosed for the formation of conductive patterns on substrates, particularly in connection with the formation of high electron mobility transistors (HEMT) and metal-semiconductor field effect transistors (MESFET). The technique allows the formation of sub-half micron conductive patterns on semiconductor substrates using optical lithography and a multilayer portable conformable mask. The method includes the application of optical contact lithography to a conventional photoresist followed by a deep UV flood exposure of an underlying multilayer PMGI portion. Metal is deposited on a semiconductor substrate through the mask formed by the photoresist and PMGI layers to produce sub-half micron conductive patterns.

Abstract: A binary optic lens is designed to achieve a predetermined effect on light propagating through the lens by specifying an initial lens design with a plurality of discontinuous subaperture regions, assigning each subaperture region a relative phase difference of 0 or .pi., and calculating the net intensity of light propagating through the lens by coherently summing the wave amplitudes for all of the subaperture regions at a given point in the image plane of the lens. The assigned phase difference for one of the subaperture regions is then changed and the intensity is recalculated by coherently summing the wave amplitudes for all of the subaperture regions at the given point. If the intensity increases over the previously calculated intensity, the changed phase difference is assigned to the selected subaperture region. The steps of changing, recalculating, and assigning are repeated for all of the subaperture regions to make one complete pass through the lens.

Abstract: A three dimensional positron emission tomography system is used in conjunction with a short lifetime positron emitter introduced into a test object to function as a tracer. A plurality of high density, high atomic number scintillating crystals are positioned within a cylindrical volume surrounding the test object, each such crystal being adapted to emit visible light in response to absorption of a gamma ray photon emitted when a positron from the tracer annihilates with an electron within the test object. A plurality of visible light photon counters is provided, with each such counter associated with one of the scintillating crystals such that the emission of visible light from the crystal is detected by the counter. Electronic circuitry sequentially polls the plurality of counters and compiles data indicative of the time at which a visible light photon was detected by each photon counter.

Abstract: A non-inverting gallium arsenide depletion mode latch circuit is responsive to high and low input data, and to clock pulses from a clock having high and low pulses for loading data and for translating data from the input to the output in a single gate delay. The circuit includes a pair of pull-up FETs having their conduction paths connected in parallel with an output node in circuit with the FETs for output data. A positive feedback path is enabled from one of the FETs for reinforcing the data at the output node. The one FET enables the feedback path during clock pulses in the low direction, while the other FET applies data to the node during high clock pulses. Data input FETs enable and disable the other FET in accordance with the input data and selective clock pulses, while a clock pulse input FET enables and disables the one FET in accordance with the clock pulses.

Abstract: A tunable electromagnetic filter includes a type II superconducting medium which exhibits a permanent ferromagnetic component after exposure to a magnetic field. A magnetic field passes through the medium in a first direction, while an input conductor wound around the medium in a second direction perpendicular to the first direction receives an input signal, and an output conductor is wound around the medium in a third direction perpendicular to the first and second directions. At resonance of the medium, an alternating field magnetic component perpendicular to both the incoming signal and the magnetic field is created to induce a current of the resonant frequency in the output conductor.

Abstract: An optical image enhancer includes a beam of coherent light for carrying an input image and a first lens for receiving the beam and performing a spatial Fourier transform of the input image. A photorefractive crystal at the Fourier plane receives the transformed image, while a coherent pump beam illuminates selected spatial frequency components of the transformed image at the Fourier plane, thereby transferring energy to the selected frequencies by two-beam coupling. A second lens receives the transformed image from the Fourier plane and performs a spatial Fourier transform of the transformed image, thereby reproducing the input image in an output image which contains intensified features corresponding to the selected spatial frequency components. A spatial light modulator may be used to cause the pump beam to illuminate the selected spatial frequency components of the transformed image at the Fourier plane.

Abstract: An optical modulator having a waveguide region comprising first and second layers of material having differing effective masses for free charge carriers at a predefined band edge energy disposed immediately adjacent to each other and covered by a lower refractive index cladding. A preferred embodiment employs a semiconductor system such as Al.sub.y Ga.sub.1-y As for the first and second material layers with the value of y adjusted between the layers so that the conduction band edge energies of the direct band in one layer is about the same as that of the indirect condition band in the other layer. A mechanism is provided for moving charge carriers between the first and second layers, such as metal contacts and a power source for applying electrical fields to the waveguide structure in a desired modulation pattern. The material layers may be deposited as a series of quantum wells with limited disordering or a ridge structure used to obtain lateral confinement.

Abstract: A planar matrix of display picture elements is operated by supplying power to the picture elements by a high current planar drive electrode connected to the picture elements, and a planar counter electrode slightly separated from the picture elements' display dots, and by addressing the picture elements with low current leads parallel to the plane of the matrix. The planes of the electrodes are parallel to the plane of the matrix. The elimination of high current power leads improves response time and resolution. The separation of the counter electrode from the display dots eliminates the need to refresh the picture elements. An isolation transistor in series with the drive transistor allows simultaneous color change of the entire matrix by simultaneous turning on and off of all isolation transistors.

Abstract: A device is provided for converting optical digital signals to electronic analog signals. A light beam is passed through a series of beam splitters. The transmission coefficient of each beam splitter is equal to the reciprocal of the base of the number of the electronic digital input signal. The beam splitters are arranged in series with the light beam so that the reflected portion of the beam is weighted to be proportional to the significance of a place in the binary number corresponding to its beam splitter. The reflected portion of the beam from each beam splitter is separately modulated in response to an input electronic digital signal for the place in the digital number corresponding to its beam splitter. The reflected portions of the beam from each beam splitter are combined and the combined beam is received by a detector which provides an electronic output which is an analog representation of the digital signal.

Abstract: An asymmetric ring laser gyroscope includes a laser gain medium for generating a clockwise beam of coherent light and a counterclockwise beam of coherent light, such that the counterclockwise beam is parallel but oppositely directed with respect to the clockwise beam. At least three reflectors constrain the clockwise and counterclockwise beams to propagate in a closed path. A means for detecting the frequency difference between the clockwise and counterclockwise beams is provided. An acentric photorefractive plate is positioned within the closed path such that the c-axis of the plate is parallel to the clockwise and counterclockwise beams in the plate.

Abstract: A neural network determines optimal control inputs for a linear quadratic discrete-time process at M sampling times, the process being characterized by a quadratic cost function, p state variables, and r control variables. The network includes N=(p+r)M neurons, a distinct neuron being assigned to represent the value of each state variable at each sampling time and a distinct neuron being assigned to represent the value of each control variable at each sampling time. An input bias connected to each neuron has a value determined by the quandratic cost function for the variable represented by the neuron.

Abstract: A nonlinear optical receiver includes a source of coherent light of frequency .omega. for illuminating a spatial region. The portion of the source light which is reflected from objects within the spatial region constitutes a signal beam. A reference beam of coherent light of frequency .omega. is also provided. A photorefractive element receives the signal and reference beams and amplifies the signal beam by two-wave mixing.The receiver may include a first polarizer, having a first polarization direction, placed between a cubic photorefractive element and the signal and reference beams, and a second polarizer, having a second polarization direction perpendicular to the first polarization direction, placed so that the amplified signal beam must pass therethrough. A frequency shifting element, such as a Bragg cell modulator, is used to change the frequency of the reference beam.