Abstract: The tensorial nature of the nonlinear constant or the electro-optic coefficient of the phase conjugate material makes it impossible to perform true phase conjugation of fields with arbitrary polarization states, i.e., to recover the polarization state of the incident light of arbitrary polarization after the phase conjugation. It is demonstrated here that an optical wave propagating through a polarization and mode scrambling medium can regain its original polarization state after phase conjugation followed by reverse propagation through the polarization and mode scrambling medium. Such polarization recovery is achieved even while a magnetic field is applied to the medium, but with power loss proportional to the magnitude of the magnetic field.

Abstract: A method of providing an optoelectronic device is disclosed in which the spatial gain profile within the device is tailored by a predetermined pattern of injecting and noninjecting contacts over the surface of the device with variation in the fractional surface coverage per unit area of injecting to noninjecting contact, thereby providing nearly arbitrary two-dimensional spatial gain profile within the optoelectronic device. A tailored gain broad area semiconductor laser fabricated by this method is capable of high power operation with very narrow, single lobed farfield patterns.

Abstract: Real time "exclusive or" operation, image subtraction, intensity inversion, and first- and second-order differentiation is achieved by an interferometer with a phase conjugate mirror for retroreflection of two or more beams derived from a single beam by a beam splitter and recombined interferometrically by the beam splitter.

Abstract: An array of nonuniform semiconductor diode lasers with supermode control for achieving a single-lobed farfield pattern is described. This is accomplished by spatially segregating the fundamental supermode from the other supermodes, tailoring the spatial gain profile as as to favor the fundamental supermode, and sufficiently increasing the intechannel coupling so as to bring about single-lobed farfield operation. In a preferred embodiment, this is achieved in a shallowly proton implanted, tailored gain, chirped laser array in which the widths of the lasers are varied linearly across the array.

Abstract: Two or more parallel waveguide lasers of different effective length are coupled together by their evanescent waves such that the composite structure functions as a single cavity having a longitudinal mode with resonances related to the resonances of the separate cavities. A very strong selection of the composite operating frequency, and suppression of most or all of the other longitudinal modes, with frequency tuning of the composite structure (both continuously and by mode hopping), can be accomplished by varying the relative currents supplied to each laser. Upon holding one cavity at one current level for a selected operating point and shifting the other, bistable operation can be achieved.

Abstract: High transconductance vertical FETs are produced in III-V epitaxially grown layers doped n, p and n, with the in-between submicron (0.15 .mu.m) layer serving as the FET channel. The layer on the drain side of the channel may be thicker (3 .mu.m) than on the source side (1.5 .mu.m). The structure is V-grooved to expose a nearly vertical surface that is Si implanted or regrown with graded n-type GaAs/GaAlAs before a gate contact is deposited on the vertical structure. An alternative to employ a heterostructure with GaAlAs layers for the source and drain, and GaAs for the channel layer. Graded GaAs/GaAlAs is then selectively regrown in the channel layer.

Abstract: Alternating layers of N+ GaAs (80 .ANG.) and N+ Ga.sub.1-x Al.sub.x As (300 .ANG.), all heavily doped with a uniform flux of Sn, and biased by 2V, provide a multiple quantum-well heterojunction structure for infrared detection with cutoff wavelength established by the choice of the value x which defines the depth of the wells. Fine tuning of the cutoff wavelength may be achieved by varying the bias voltage. By biasing the individual quantum-well layers progressively through a voltage divider, an avalanche mechanism may be achieved in the detector for signal amplification. The detectors may be fabricated in large two-dimensional arrays.

Abstract: An integrated laser structure for paired stripe semiconductor lasers is provided with separate current control of each stripe laser. With optical coupling between the lasers, one of the lasers is operated below threshold and serves the longitudinal mode selection and tunability of the other laser, thereby to obtain a single longitudinal mode operation. Without coupling, the paired-laser structure operates as a source of two independent wavelengths.

Abstract: A two-segment contact buried heterostructure (BH) laser is pumped by a current applied to its absorber contact from a source of high impedance on the order of 100K.OMEGA. or more. The parasitic resistance between the absorber contact and the gain contact is high on the order of 10K.OMEGA.. For a given absorber (bias) current the laser exhibits a relatively wide hysteresis on the order of 1 mA or more in the light vs. gain contact current. Such a laser is highly useful as a bistable optical element. The laser is also bistable with selected pump gain and absorber currents to exhibit a wide hysteresis of voltage across the absorber contact vs. relative amounts of light which is reflected back to the laser as feedback. The laser serve both as a light source and as a detector for reading out binary information stored as light reflective spots on a medium, e.g. a video disk.

Abstract: A passive (self-pumped) phase conjugate mirror uses a third-order nonlinear polarization medium, either of the refractive type (effective nonlinear) or the actual nonlinear type, with an optical system of one or more mirrors to reflect back through the medium a coherent incident beam diffracted by the medium. With two mirrors, they may be aligned to form a linear optical cavity containing the nonlinear medium, or they may be so oriented on one side of the medium that the incident beam transmitted through the medium is reflected back through the medium at an angle with the incident beam, and diffracted light from the incident beam is reflected back through the medium in the opposite direction coincident with the incident beam. A passive phase conjugate mirror may replace an end mirror of an optical cavity for a laser gain medium. Phase distortions of the laser beam in the laser cavity are corrected by the passive phase conjugate mirror.

Abstract: An arrangement for damping the resonance in a laser diode includes an additional layer (25) which together with the conventional laser diode form a structure (35) of a bipolar transistor. Therein, the additional layer serves as the collector, the cladding layer (12) next to it as the base, and the active region (11) and the other cladding layer (13) as the emitter. A capacitor (30) is connected across the base and the collector. It is chosen so that at any frequency above a certain selected frequency (f.sub.c) which is far below the resonance frequency (f.sub.res) the capacitor impedance is very low, effectively shorting the base to the collector.

Abstract: An optical fiber cable and magnetic field detector magnetostrictively reave to the presence of an external magnetic field is presented, and methods thereof. The optical fiber cable comprises a elongated optically transparent core sheathed by a magnetostrictively responsive jacket disposed about the periphery of the core. The jacket responds to magnetic fields present and strains the core effecting the light transmission of the core. The effect upon the light transmission by the jacket is detected by interferometry for determining the presence of the magnetic field.

Abstract: Solid state electro-optical devices are formed on a semi-insulating substrate, with all contacts of each device being on the same side of the substrate. These devices include two types of lasers, one operating on current crowding effect and the other by lateral diffusions. Either type laser is integratable with an electronic device e.g. a Gunn oscillator or an FET on the common semi-insulating substrate to form a complex monolithic electro-optical device.

Abstract: A laser which self-corrects for distortions introduced into the laser beam wavefronts by aberrations and time-varying phenomena internal to the laser. The improved laser includes a partially transmissive first reflecting element, an aperture stop, a lasing medium and a nonlinear phase conjugate reflecting device as the second reflecting element. During laser operation, aberrated wavefronts impinging upon the second reflecting element are reflected as the phase conjugate waveform thereof. The aperture stop restricts laser operation to the fundamental mode which allows only corrected, unaberrated waves to pass through the aperture stop and to subsequently exit the laser. Four embodiments are described utilizing stimulated Brillouin scattering (SBS), four-wave mixing, three-wave mixing and photon echo devices as the second reflecting element.

Abstract: Solid state electro-optical devices are formed on a semi-insulating substrate, with all contacts of each device being on the same side of the substrate. These devices include two types of lasers, one operating on current crowding effect and the other by lateral diffusions. Either type laser is integratable with an electronic device e.g. a Gunn oscillator or an FET on the common semi-insulating substrate to form a complex monolithic electro-optical device.

Abstract: In the disclosed parametric frequency converter a dc electric field is utilized to remove spatial inversion symmetry of NH.sub.2 D gas molecules contained in a Stark cell. Simultaneous introduction into the Stark cell of a laser beam at a frequency f.sub.1 (e.g., corresponding to about 10.6 .mu.m) and microwaves at a frequency f.sub.2 (e.g., about 4.1 GHz) produces resonantly enhanced parametric mixing of the frequencies f.sub.1 and f.sub.2, resulting in the generation of a laser beam at the difference frequency f.sub.3 = f.sub.1 - f.sub.2.

Abstract: Disclosed is a process for fabricating small geometry electronic devices, including a variety of integrated optical devices. The process includes the steps of holographically exposing a resist masking layer to a plurality of optical interference patterns in order to develop a masking pattern on the surface of a semiconductive body. Thereafter, regions of the body exposed by openings in the masking pattern are ion beam machined to thereby establish very small dimension undulations in these regions. These closely spaced undulations have a variety of uses in optical devices as will be described. The present invention is not limited to the geometry control of semiconductive structures, and may also be used in the geometry control of metallization patterns which have a variety of applications, or the geometry control of any ion beam sensitive material.

Abstract: An X-ray laser comprises a single crystal in the form of a thin film with an oriented set of prominent atomic planes so that when the crystal is pumped, X-ray photons which are emitted from one of the atomic constituents of the crystal, experience internal feedback (Bragg scattering) from the atomic planes thereby eliminating the need for external feedback. In addition the crystal functions as a thin planar waveguide confining the X-ray waves therein, thereby reducing the necessary pumping power and increasing overall efficiency.

Abstract: There is disclosed an integrated optical detector comprising a semiconductor substrate having an optical waveguide formed integrally therewith and a photodetector made from the same semiconductor material as the waveguide and integrally coupled to it. The detector region is sensitive to light of the same wavelengths that can be transmitted through the waveguide region of the semiconductor without excessive absorption therein by virtue of the fact that after the waveguide is formed proton bombardment of the detector portion thereof is used to create optically active defect centers thereby shifting the effective absorption edge in the detector region. Where gallium arsenide is used as the semiconductor defect levels induced by implantation of high energy protons give rise to optical absorption between 6 micron and 0.9 micron. This results in detector action in the presence of a Schottkey barrier depletion layer.