Rockwell International Corporation

Pochi A Yeh

Mohsen Khoshnevisan

John H Hong

Mark D Ewbank

John M Tracy

William J Gunning, Iii

Jack L Feinberg

Ian C McMichael

Tallis Y Chang

John P Eblen, Jr

Arthur E Chiou

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.

Flexible rejection filter (U)

Holographic apparatus and methods are provided for generating high resolution telescopic images using low cost, small aperture lenses. Holographic media, such as photorefractive crystals, are used in conjunction with multiple and/or synthetic aperture techniques. In a multiple aperture system, a thin nonlinear holographic medium is used with a plurality of small optical lenses to compensate for the inherent piston and tilt errors of the lenses, thereby providing higher resolution. In another embodiment, synthetic aperture techniques are accomplished by illuminating a far field object with coherent light, deriving a reference beam from the coherent light, and changing the position of the reference beam in accordance with a computational formula. A hologram is formed from a sequence of image exposures in the holographic media, each made at different positions with respect to the image. The sequence of exposures is combined and phased in the holographic media to synthesize a high resolution image normally achievable only with a relatively larger aperture.

Holographic techniques for generating high resolution telescopic images

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. The values of the first and second refractive indices and thicknesses are such that the phase retardation of the multilayer is equal in magnitude but opposite in sign to the phase retardation of the liquid crystal layer in its homeotropically aligned state over a predetermined range of viewing angles.

Compensator for liquid crystal display, having two types of layers with

An optical system is provided for the transformation of input images to be correlated by a pattern recognition system. A pulse of light from a laser carries an input image to a beam splitter. The beam splitter divides the input pulse into an output pulse and a thoughput pulse that is directed through an optical ring resonator. The ring resonator is an optical reimaging system that transforms the input image in scale or orientation. The transformed version of the input image is then directed to the beam splitter where it is split into a modified output pulse and a modified throughput pulse that reenters the ring resonator. The transformation process is self-repeating to generate a series of successively modified output images that are equally spaced in time. The series of output images can be provided to an optical pattern recognition system for correlation with a stored reference. The generation of successive transformations of the input image precludes the necessity of storing a large library of reference images to be matched with the input image.

Optical image transformation system

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.

Asymmetric ring laser gyroscope and method for detecting rotation with

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). The MPPC generates a spatial phase conjugate of the oscillator beam that carries the temporal characteristics of the signal beam. A beam splitter combines the information carrying phase conjugate beam with a phase conjugate of the pure local oscillator beam returned by a phase conjugate mirror. The two phase conjugate beams arrive at the plane of a photodetector with precisely the same wave front and direction. The matched wave fronts produce high heterodyne efficiency, and the automatic tracking feature of the phase conjugators provides a wide field of view.

Optical heterodyne detector

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. pa A first laser may provide both the source of coherent light and the reference beam of coherent light, or a first laser may provide the source of coherent light while a second laser provides the reference beam of coherent light. The photorefractive element may be a cubic photorefractive crystal or a nonlinear optic material. A two dimensional focal plane array may be added for detecting the amplified signal beam.

Nonlinear optical doppler imaging amplifier

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. If the average intensity of the dirty beam is much higher than that of the CW beam, only a small fraction of the dirty beam needs to be directed into the MPPC for beam clean-up. The larger fraction of the dirty beam can be directed into a photorefractive crystal for two-beam coupling with the clean beam output by the MPPC. By means of photorefractive two-beam coupling, energy from the dirty high power beam serves to amplify the clean beam, thereby improving the overall energy efficiency of the laser beam clean-up system.

Laser beam clean-up using mutually pumped phase conjugation

An apparatus for subtracting the amplitude of a first optical image on a first beam from the amplitude of a second optical image on a second beam includes a first beam splitter to divide the first beam into a first transmitted beam and a first reflected beam and to divide the second beam into a second transmitted beam and a second reflected beam. The first transmitted beam and the second reflected beam combine as a first mixed beam, while the first reflected beam and the second transmitted beam combine as a second mixed beam. A pinhole removes spatial information from the second mixed beam. The first and second mixed beams interfere within a nonlinear medium to create a composite hologram. A coherent reference beam directed at the nonlinear medium reads the interference pattern, so that the difference between the first and second images is superimposed on the reference beam emerging from the nonlinear medium. A second nonlinear medium may be used to retroreflect one of the mixed beams toward the nonlinear medium as the reference beam, in which case the pinhole is not required.

Real-time optical image subtraction

An intensity inverter includes an optically nonlinear medium and a reference beam having a uniform transverse intensity distribution and having the same wavelength as the signal beam. The reference beam is directed into the nonlinear medium. A readout beam having the same wavelength as the signal beam and counterpropagating with respect to the reference beam is also directed into the nonlinear medium. When the signal beam is directed into the nonlinear medium, the signal beam and the reference beam interact to form a hologram within the nonlinear medium, thereby diffracting a portion of the readout beam, the undiffracted portion of the readout beam having imposed on it an inversion of the signal.

Real time image inversion using four-wave mixing

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. Selecting the light source and changing the data pattern provide additive and subtractive weight change capability for implementing various learning algorithms.

Adaptive optical neural network

An apparatus for steering a coherent input beam of electromagnetic energy includes an optically nonlinear medium for positioning in the path of the input beam. A source of acoustic energy generates acoustic waves in the nonlinear medium with a predetermined frequency and direction. The frequency and direction of the acoustic waves are selected to diffract a portion of the input beam as an output beam at a predetermined angle with respect to the input beam, interference between the input beam and the output beam initially causing an electrostrictive grating to form in the medium, with the grating subsequently causing additional energy to be transferred from the input beam to the output beam by stimulated Brillouin scattering.

Kerr-Bragg agile beam steering device

A beam of coherent light is coupled into an array of light detectors using a beam splitter for dividing the beam into a probe beam and a pump beam and a spatial light modulator for varying the intensity of the probe beam in a first direction perpendicular to the direction of propagation of the beam. A photorefractive element is positioned to receive the modulated probe beam and the pump beam, the beans being oriented with respect to the photorefractive element and with respect to each other such that photorefractive two-wave mixing within the photorefractive element nonreciprocally transfers energy from the pump beam to the modulated probe beam, which is then detected by the detector array. A first lens system may be positioned in the path of each probe beam between the beam splitter and the spatial light modulator for expanding each probe beam in the first direction, while a second lens system may be positioned in the path of each pump beam between the beam splitter and the photorefractive element for expanding each pump beam in the first direction.

Reconfigurable 0ptical interconnect using dynamic hologram

A nonlinear optical matrix multiplier includes a nonlinear optical medium with a first optical input beam impinging on the medium, the transverse spatial intensity of the first input beam being modulated by a first two dimensional matrix. A second optical input beam impinges on the medium, with the transverse spatial intensity of the second input beam being modulated by a second two dimensional matrix. An optical probe beam impinges on the medium, the first input beam, the second input beam, and the probe beam being oriented with respect to one another and with respect to the medium such that the beams interact within the medium by means of four-wave mixing. A diffracted output beam emerges from the medium, with the transverse spatial intensity of the output beam modulated by the product of the first and second matrices.

Nonlinear optical matrix manipulation

A coupled laser system includes a plurality of substantially parallel beams of coherent radiation with an output beam of coherent radiation at an oblique angle with respect to the plurality of beams. A photorefractive element is positioned to receive the plurality of beams and the output beams, the beams being frequency locked to within the photorefractive bandwidth of the photorefractive element such that laser energy is diffracted from the plurality of beams to the output beam by means of two-wave mixing. A lens may be used for focussing the parallel beams in the photorefractive element, while a plurality of mirrors may be supplied for adjusting the orientation of the output beam within the photorefractive element. Another coupled laser system includes a plurality of lasers, each laser providing a beam of coherent radiation, an optical resonant cavity, and a photorefractive element positioned within the resonant cavity, the beam being frequency locked to within the photorefractive bandwidth of the photorefractive element such that laser energy is diffracted from the coherent beams to a coupling beam in the resonant cavity by means of two-wave mixing. The resonant cavity is defined by a unidirectional ring resonator, with a partially reflecting mirror, a first substantially 100% reflecting mirror, and a second substantially 100% reflecting mirror.

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Thousand Oaks, CA, United States of America

Pochi A Yeh