Abstract: An optical modulator having a voltage—optical output characteristic in which optical output varies periodically with respect to a voltage value of an electrical drive signal is driven by a modulator driving voltage signal, which has an amplitude of 2·V&pgr; between two light-emission culminations or two light extinction culminations of the voltage—optical output characteristic. A low-frequency superimposing unit superimposes a prescribed low-frequency signal on the modulator driving voltage signal, and an operating-point controller controls the operating point of the optical modulator by detecting operating-point drift of the optical modulator based upon the low-frequency signal component contained in an optical signal output from the optical modulator and controlling the bias voltage of the optical modulator in dependence upon the drift of the operating point of the optical modulator.

Abstract: Disclosed herein is a method for wavelength conversion. In this method, an optical signal received is separated into a first polarization component having a first polarization plane and a second polarization component having a second polarization plane perpendicular to the first polarization plane. The first polarization component is supplied to a first optical waveguide structure over which a first surface acoustic wave propagates, in a direction identical with the propagation direction of the first surface acoustic wave. The second polarization component is supplied to a second optical waveguide structure over which a second surface acoustic wave propagates, in a direction opposite to the propagation direction of the second surface acoustic wave. First converted light output from the first optical waveguide structure and second converted light output from the second optical waveguide structure are combined together.

Abstract: A polarization device includes a reflection-type polarization element disposed at a side to which an optical beam comes in and an absorption-type polarization element disposed behind the reflection-type polarization element, wherein the reflection-type polarization element and the absorption-type polarization element are disposed such that a transmission axis of the reflection-type polarization element coincides with the transmission axis of the absorption-type polarization element. Further, an optical projector using such a polarization device is disclosed.

Abstract: An optical display system includes a source of white uncollimated light, a color separator for separating the white light into spectral components, a reflective ferroelectric light valve for spatially modulating the spectral components, and a polarizing beam splitter for directing vertically polarized light towards a display lens. The system further includes a corrective film disposed in an optical path between the white light source and the light valve. The film, which may be made of a ferroelectric material or other birefringent material, ensures that retardance of the light valve is approximately 180 degrees or some other desired angle over a spectrum of interest. In this manner, the light valve is achromatized by the film.

Abstract: An imaging device comprising an electro-optic modulator for modulating incident laser beams; an array of adjacent electrodes comprising a group of imaging electrodes addressed in accordance with image information; means to illuminate an area slightly larger than the width of said imaging electrodes; and one or more additional electrodes located on each side of said group of imaging electrodes to permanently direct extraneous marginal beams to light-stop means so that only the light emerging from the imaging electrodes is allowed to reach a light sensitive medium.

Abstract: An apparatus and a method for stepper exposure control by utilizing a shutter assembly formed of electro-optic crystal materials in a photolithographic process are disclosed. In the apparatus, a series of control panels are stacked together to form a shutter assembly. Each of the control panel is formed by depositing a multiplicity of parallel, spaced-apart lines of electro-optic crystal material on a polarizer sheet. Two of such polarizer sheets are then stacked together with the lines parallel to each other and the lines on the top panel overlapping the spacing on the bottom panel. Two bottom panels are formed similarly however, positioned with the lines perpendicular to the lines in the first and second control panel when assembled together in the shutter assembly. A suitable electro-optic crystal material used should withstand a high temperature environment. One of such suitable material is LiNbO3.

Abstract: A solid state device used to modulate the intensity of reflected or transmitted light by modulating with an external voltage the optical thickness of a thin film ferroelectric placed in an etalon cavity is disclosed. The device is constructed by selecting a generally planar supporting substrate, preferably silicon or sapphire in order to be compatible with silicon integrated circuits. A dielectric stack consisting of alternating layers of different index of refraction materials, also specifically selected to be compatible with later growth of the thin film ferroelectric, is deposited thereon to form a partially reflective and partially transmitting mirror, followed by a transparent electrically conductive layer. The thin film ferroelectric is deposited on the conductive layer, followed by a second transparent conductive layer and a second dielectric stack. Leads are connected to the conductive layers and in turn to a voltage generator.

Abstract: A polarization conversion system comprises a polarized light selective reflector that divides incident unpolarized light into first and second types of polarized light, transmits the first type of polarized light and reflects the second type of polarized light, a relay optical system that relays an incident light beam onto the polarized light selective reflector, a polarized light reflector, disposed on an optical path of a reflected light beam reflected by the polarized light selective reflector, that reflect the reflected light beam back to the polarized light selective reflector while converting the second type of polarized light to polarized light of the first type.

Abstract: An optical-fiber-amplifier measuring apparatus includes: a light source 14 for measuring various characteristics of an optical fiber amplifier 22 to be measured; an acoustooptic modulator 16 for modulating an optical signal inputted from the light source 14 to the optical fiber amplifier 22 to be measured; a light source 10 for setting the optical fiber amplifier 22 to be measured in a saturated state; and an acoustooptic modulator 12 for modulating an optical signal inputted from the light source 10 to the optical fiber amplifier 22 to be measured.

Abstract: A multi-mode stereoscopic imaging system is described. It is the first stereo system which is convertible back and forth from the auto stereo viewing mode without glasses to the binocular stereo viewing mode with glasses. It is based on micro-polarizer arrays and spatial multiplexing of images. The system consists of a stereo image component and an auto parallax barrier component. Both components use the properties of &mgr;Pols. Switching from one mode to the other is accomplished manually, and electronically with the aid of a liquid crystal light valve. The system combines the benefits of auto-stereo imaging and the binocular stereo imaging of prior art techniques without their limitations.

Abstract: Broad wavelength tuning range are achieved in an effectively reset-free, optical, automatic polarization controller by providing a device and method for varying the polarization of an input beam of light. A block of electro-optic material has two pairs of electrodes for applying a voltage across the block. Light is launched into an input end of the block for receiving the input beam of light. A controller controls a quadrature voltage applied to the first and a second pair of electrodes; the quadrature voltage has the form of a magnitude and an angle. The quadrature voltage can be varied in such a manner as to orient a given electric field within the electro-optic material through a plurality of angles, for example between 0 and 2&pgr; radians; the magnitude of the quadrature voltage can be set to create an arbitrary retardance from 0 to 2&pgr;. Any output polarization state can be realized by appropriately varying the magnitude and angle of the voltage applied to the Vx and Vy electrodes.

Abstract: A tunable optical wavelength selective filter is constituted by a dynamic holographic diffraction element (3) in combination with a fixed diffraction grating or hologram (2). The dynamic diffraction element (3) is preferably implemented as an electronically controlled image displayed on a pixelated spatial light modulator and in particular a spatial light modulating using photo-electronic integrated circuits fabricated using silicon VLSI technology and integrated with ferro-electric liquid crystals. Amongst other uses the filter can be implemented to form a digitally tunable laser.

Abstract: A photochromic composition which develops a neutral tint such as grey, green, brown or amber upon the irradiation with light including ultraviolet rays such as sunlight starting from the initial colorless state, maintaining a homogeneous color tone in the transient stage of developing color. The photochromic composition comprises 100 parts by weight of a fulgimide compound and/or a fulgide compound, and from 10 to 300 parts by weight of a chromene compound having a molar extinction coefficient of not smaller than 150 L/mol-cm for light of a wavelength of 400 nm.

Abstract: A programmable wavelength router having a plurality of cascaded stages where each stage receives one or more optical signals comprising a plurality of wavelength division multiplexed (WDM) channels. Each stage divides the received optical signals into divided optical signals comprising a subset of the channels and spatially positions the divided optical signals in response to a control signal applied to each stage. Preferably each stage divides a received WDM signal into two subsets that are either single channel or WDM signals. A final stage outputs optical signals at desired locations. In this manner, 2.sup.N optical signals in a WDM signal can be spatially separated and permuted using N control signals.

Abstract: Disclosed is an electromagnetic beam polarizer system which provides a sequential combination of a Brewster Angle and other than Brewster Angle polarizer system in combination with reflective mirrors, which elements are arranged in any functional order. The electromagnetic beam polarizer system is more compact than multiple Brewster angle polarizer systems, and demonstrates a high extinction coefficient between electromagnetic radiation beam orthogonal components in use.

Abstract: Disclosed is a light shutter device comprising a plurality of optical element for modulating light passing therethrough. Each optical element is made of PLZT and the surface of a light modulating region of each optical element is coated with a thin film. The surface electrical resistance on the thin film is 10.sup.10 .OMEGA./sq or less.

Abstract: Electro-optic modulator comprises a substrate having an epitaxial, preferentially oriented, low scattering loss thin ferroelectric film waveguide deposited by metalorganic chemcial vapor deposition on the substrate, and first and second strip electrodes on the waveguide with the electrodes spaced apart to establish an electric field effective to render the waveguide modulating to light in response to applied bias or voltage.

Abstract: A retroreflecting modulator including a lens, a light guide, a light modulator, and a reflective surface. Incident light falls on the lens, where it is focused as a spot on a focal surface. The light guide transmits the focused light to the light modulator, where it is modulated and reflected back, via the reflective surface and light guide, to the lens. The lens emits the modulated light in the opposite direction as the incident light. The preferred light-receiving and focusing device is a specialty sphere lens, the preferred light guide is a fiber optic plate, and the preferred light modulator is a liquid crystal modulator. The retroreflecting modulator may be spatially-unresolvable, where a single signal modulates the light, or spatially-resolvable, where the modulation signal depends upon the direction of the incident light.

Abstract: A system for the reduction of a laser equivalent surface area and for the optical protection of an optical device including a first polarizer and a first multiple wavelength quarter-wave plate placed in series in the path of a multiple wavelength light beam between the polarizer and the optical device. This system brings into play polarized light, and associates a liquid crystal shutter with it, providing for protection against optical aggression. The entire unit may take the form of a detachable optical attachment.

Abstract: An optical shutter device wherein a light emitted from a light source is allowed to be incident to a polarization shutter chip through a fiber array and then the light is caused to pass through the chip by turning on a voltage to be applied to electrodes connected to transmittable portions corresponding to pixels, so that a receptor surface is lighted through an imaging lens array. Light which is incident to the polarization shutter chip at an angle .theta..sub.0 is reflected from electrode vertical surfaces, and then the light outgoes from the transmittable portions in the form of leakage light. However, the aperture angle of a lens unit of the imaging lens array is set smaller than the incident angle .theta..sub.0, and thus the light (which were incident) at the angle .theta..sub.0 (leakage light) is not focused on the receptor surface by the lens unit.

Abstract: The present system for redirecting a light beam makes use of a transparent pressure vessel that is filled with a compressible fluid, whose refractive index changes as a function of the pressure applied to the compressible fluid to redirect the path of a light beam that is transmitted through the transparent pressure vessel. An incident beam of coherent monochromatic light is applied to a transparent segment of a wall of the transparent pressure vessel, where this incident light beam is refracted by the compressible fluid contained in the transparent pressure vessel. The refracted light beam traverses the transparent pressure vessel and exits the transparent pressure vessel at a point along the opposite wall of the transparent pressure vessel as determined by the refractive index of the compressible fluid, which is determined by the pressure of the compressible fluid. The pressure of the compressible fluid is controlled by using a pump that is fluidically connected to the transparent pressure vessel.

Abstract: A system and method are provided for detecting one or more substances. An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. The first wavelength band and second wavelength band are unique. Further, spectral absorption of a substance of interest is different at the first wavelength band as compared to the second wavelength band. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation.

Abstract: A method and apparatus for modulating a light beam in an optical processing system is described. Preferably, an electrically-controlled polarizer unit and/or an analyzer unit are utilized in combination with a spatial light modulator and a controller. Preferably, the spatial light modulator comprises a pixelated birefringent medium such as a liquid crystal video display. The combination of the electrically controlled polarizer unit and analyzer unit make it simple and fast to reconfigure the modulation described by the Jones matrix of the spatial light modulator. A particular optical processing objective is provided to the controller. The controller performs calculations and supplies control signals to the polarizer unit, the analyzer unit, and the spatial light modulator in order to obtain the optical processing objective.

Abstract: An imaging system and method directs white light to a reflecting polarizing surface at an angle of incidence substantially equal to the Brewster angle to help maximize or greatly increase the reflected S polarized light and minimize or greatly decrease the reflected P polarized light. A contrast enhancing device also helps to reduce the reflected P polarized light. Color splitter and combining optics devices separate the reflected polarized light into a plurality of different color light components. Light modulating devices modulate each one of the color light components and rotate selectively the S polarized light and direct P polarized light toward a viewing surface. Thus, the output transmitted contrast ratio of the transmittal P polarized light to the transmitted S polarized light is enhanced.

Abstract: An object of the invention is to provide a polarization scrambler wherein the polarization of linearly polarized signal light can be rotated to facilitate obtaining a minimum degree of polarization, and wherein scrambling operation is possible even if signal light of optional polarization states is input. Accordingly with the polarization scrambler, a polarization rotation section is provided on an input side on a chip on which is formed an optical waveguide, and a polarization scrambling section is provided on an output side. With the polarization rotation section, the polarization of linearly polarized signal light which is transmitted by the optical waveguide is rotated by means of an acousto-optic effect due to an elastic surface wave generated by an electrode, so as to become 45.degree. with respect to a vertical direction of the optical waveguide.

Abstract: A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination element, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band.

Abstract: An optical fiber modulator comprises an optical fiber, a substrate having a groove pattern in which the optical fiber is fixed, and a modulation unit including a polarizer, an electrooptic element, and an analyzer aligned in a light path of the optical fiber in this order, wherein the electrooptic element is made of a poled portion of the optical fiber, and when the electrooptic element is in an electric field-free condition, an absolute value, .delta., of a phase difference of a beam passed through the electrooptic element is within the following range(m/2-1/6).pi..ltoreq..delta..ltoreq.(m/2+1/6).pi.wherein m is an odd number. When the portion of the optical fiber is poled from two different directions, the modulation unit should further include a wave plate, and an absolute value, .delta.1, of a phase difference of a beam passed through the wave plate and the electrooptic element is within the following range of (n/2-1/6).pi..ltoreq..delta..ltoreq.(n/2+1/6).pi. wherein n is an odd number.

Abstract: A method and apparatus for overcoming polarization induced signal fading in both heterodyne communication and interferometric sensing. An adjustable birefringent element in series with a linear-polarization beam splitter forms an elliptical-polarization beam splitter. The birefringent element controllably evolves the states of polarization of two input signals thereby controlling the power contribution of each signal onto the orthogonal axes used by the linear beam splitter. When the states of polarization are evolved such that there are equal signal to reference power ratios on the beam splitter axes, subsequent detectors generate a constant, optimum amplitude signal without the need for weighting or decision circuits.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: An optical power regulator employs a variable optical attenuator having a first birefringent element that spatially separates the input optical beam into two orthogonally-polarized beams. Both beams pass through a polarization modulator (e.g., a liquid crystal material) that rotates their polarizations to an extent determined by the control voltage applied across the polarization modulator. A final birefringent element spatially separates both beams exiting the polarization modulator into two pairs of orthogonally-polarized beams (i.e., two horizontally-polarized and two vertically-polarized components). The thicknesses and optical properties of the birefringent elements are selected so that two of the four beams are combined by the final birefringent element to exit at the output port of the regulator, while the remaining two beams are blocked.

Abstract: An optical fiber of the type makes it possible to guide light waves independently of their polarization at 1.55 .mu.m wavelength. The optical layer (12) and semiconductor material (11, 12) adjacent to both flat sides (121, 122) of the layer (12) have a crystal lattice constant (1) less than 1% lower than a determined crystal lattice constant (a1) of InP. In a preferred embodiment of the invention, a superlattic is provided on an InP substrate to widen the InP lattice constants.

Abstract: An optical shutter element drive mechanism for driving optical shutter elements that are electrically equivalent to condensers by charging and discharging the elements by a power source and switching elements. The optical shutter element drive mechanism includes a resistor through which a current for charging the optical shutter elements flows when the optical shutter elements are charged and through which a current for discharging the optical shutter elements flows when the optical shutter elements are discharged.

Abstract: A split reciprocal polarization switch (SRPS) for use in constructing high performance switching devices used in fiber optics. The SRPS allows selective changes in the polarization of one or the other of two optical rays passing therethrough along first and second bi-directional ray paths of the SRPS so that they emerge therefrom with the same polarizations. The SRPS includes a switching section for selectively changing the optical polarization of optical rays according to a selected state of the switching section, and a split section including a first and second sections having different polarization changing characteristics.

Abstract: The diffractive optical modulator of the invention includes: a plate having a portion functioning as a first electrode; a spacer layer formed on the plate; and a grating consisting of a plurality of beams having a portion functioning as a second electrode, both ends of the beams being supported on the spacer layer. In the diffractive optical modulator, by adjusting a voltage applied between the first electrode and the second electrode, a distance between the beams and the plate is varied, thereby controlling the diffraction efficiency. An insulating layer is further provided between the plate and the plurality of beams.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: A programmable wavelength router having a plurality of cascaded stages where each stage receives one or more optical signals comprising a plurality of wavelength division multiplexed (WDM) channels. Each stage divides the received optical signals into divided optical signals comprising a subset of the channels and spatially positions the divided optical signals in response to a control signal applied to each stage. Preferably each stage divides a received WDM signal into two subsets that are either single channel or WDM signals. A final stage outputs optical signals at desired locations. In this manner, 2.sup.N optical signals in a WDM signal can be spatially separated and permuted using N control signals.

Abstract: An optical transmission method and device consisting of coding a binary data pattern (SI) to be transmitted in the form of a second binary signal (SM), by differential coding; filtering the second binary signal (SM) to obtain a duobinary signal (SMF having three meaningful values (-1, 0.+-..epsilon., +a) and a narrower bandwidth; and modulating an optical carrier according to the values assumed by the filtered signal (SMF), the modulated carrier having a maximal amplitude to represent the maximal value (+a) and the minimal value (+a) of the duobinary signal (SMF), the phase of the modulated carrier being shifted by .theta..sub.1 and .theta..sub.2 =.theta..sub.1 +180.degree., respectively, and a minimal amplitude to represent values (0.+-..epsilon.) near 0 if the duobinary signal. The method of this invention is suitable for long distance fiber-optic transmissions.

Abstract: A liquid-crystal cell having plates defining a gap between them which is filled with a liquid crystal, especially a twisted nematic. The plates are made non-parallel to a predetermined degree so that the liquid crystal assumes a wedge shape, producing different effective thicknesses of the liquid crystal depending on the lateral position within the cell. In use, a narrow beam irradiates a portion of the cell, and the cell is positioned along the wedge direction so as to optimize the cell performance. The invention is particularly useful with a liquid-crystal multi-wavelength switch, which requires extinction ratios between the two states of the cell.

Abstract: A photostrictive device controller and a photostrictive device control method, which can produce a fast response without causing a sharp temperature rise when driving the photostrictive device. The photostrictive device controller comprises: a light source 2 for applying light to the photostrictive device 1 that, upon receiving light, produces a photostrictive effect; an illumination optics 3 for introducing light from the light source 2 onto the photostrictive device 1; and a control device 4 for controlling the energy density of light applied to the photostrictive device 1. The control device 4 of the controller controls the illumination optics device 3 to lower, at a point close to where the photostrictive effect of the photostrictive device 1 is saturated, the energy density of the irradiated light to a level at which the elongation caused by heat can be ignored.

Abstract: In an electro-optic voltage transducer utilizing a crystal exhibiting birefringence in a fast axis and a slow axis mutually orthogonal to an optic axis in the presence of an electric field produced by the voltage to be measured, the crystal is mounted for angular adjustment relative to the direction of propagation of a light beam passing through the crystal and polarized at an angle to the fast and slow axes to provide adjustment of the effective half-wave voltage of the crystal. Preferably, the crystal is a disk mounted for rotation about an axis perpendicular to the optic axis by temperature sensitive mounts extending perpendicular to radii of the disk in order to provide temperature compensation. Greater angular adjustment, which extends unambiguous voltage measurement above the natural half-wave voltage of the crystal, is provided by securing the temperature responsive mounts to a rotatable support disk.

Abstract: A signal processing system processes an input signal in real time. The system includes a light valve array for selectively attenuating light incident thereupon in response to electronic control signals, a light source for providing illumination, a light-sensitive array for producing electronic output signals representing a processed version of the input signal in response to light incident thereupon, and control circuitry for generating and applying electronic control signals to the light valve array in response to the input signal. The electronic control signals are generated from the input signal and are adapted for implementing an arbitrarily-selected signal processing operation. The light valve array is situated between the light source and the light-sensitive array, such that the light source is selectively attenuated by the light valve array, and such that the selectively attenuated light is incident upon the light-sensitive array.

Abstract: A liquid crystal-polymer composite film comprising (1) a high-molecular weight compound containing at least one kind of monomer units providing a side chain having a liquid crystal nature and at least one kind of monomer units providing a side chain having no liquid crystal nature and (2) a low-molecular weight liquid crystal, the high-molecular weight compound (1) and the low-molecular weight liquid crystal (2) being in separate phases, and the monomer units providing a side chain having no liquid crystal nature being crosslinked; and an electro-optical element comprising a pair of substrates each having an electrode having interposed therebetween a liquid crystal-polymer composite film comprising (2) a low-molecular weight liquid crystal and (1) a high-molecular weight compound in separate phases, the substrates each having a surface comprising a material having a reactive group on the side in contact with the composite film, the reactive group being chemically bonded to the high-molecular weight compound (

Abstract: A polarization insensitive electro-optic modulator is constructed by providing a polarization beamsplitter to separate an incoming light beam into two orthogonally plane polarized beams. Each of the polarized beams passes through a separate electro-optic modulator where each beam is modulated by the same data signal. After modulation the beams are combined to yield a modulated beam having modulated components that are orthogonally polarized. Not only is this device insensitive to changes in polarization of the input beam, the final modulated beam can be detected by optical receivers without regard to polarization alignment of the modulated beam and the receiver.

Abstract: A method and apparatus for counteracting polarization fading and stimulated Brillouin scattering in long runs of non-polarization maintaining optical fiber. A linearly polarized optical signal is depolarized by phase modulating the signal at a frequency significantly above the fiber's Brillouin scattering linewidth V.sub.b prior to launch into the long run of fiber.

Abstract: An optical polarization controller comprises a polarization control element, a polarizer, a light divider and a photo-detector. The polarization control element rotates a plane of polarization of an Input signal light by a rotation angle in a predetermined rotational direction and outputs the result as a rotated signal light. The polarizer extracts a component of the rotated signal light having a predetermined plane of polarization and outputs the component as a polarized signal light. The light divider divides the polarized signal light into a plurality of polarized signal lights which have the same planes of polarization as the plane of the polarized light outputted by the polarizer. The photo-detector detects a level of one of the plurality of polarized signal lights and supplies a control signal indicating the level to the polarization control element.

Abstract: In a photostrictive device whose light-irradiated surface is irradiated with a beam of light with a specified wavelength to produce a photostrictive effect, the light-irradiated surface is formed with a surface roughness Ra related to the wavelength of light. This increases the light absorption of the photostrictive device, thereby improving the responsiveness.

Abstract: The ellipticity of a thermal lens is controlled in a diode-pumped anisotropic crystal, such as Nd:YVO4. The crystal has two opposing optical end faces through which a pump beam and an output beam pass. The crystal also has opposing "c" axis crystal faces normal to a "c" axis of the crystal, and opposing "a" axis crystal faces that are normal to an "a" axis of the crystal. A mount supports the crystal and serves as a heat sink. A path is created to conduct heat from the crystal through the "c" faces, while the "a" faces are thermally isolated from heat conduction. The thermal lens ellipticity is controlled in order to produce a round, diffraction limited gaussian beam suitable for applications that require a high power, good quality beam from a simple, reliable laser source.

Abstract: The invention realizes an optical modulator which prevents occurrence of an edge breakdown and is improved in extinction characteristic and voltage resisting property. The optical modulator comprises an oxide film formed as a growth inhibiting film on a compound semiconductor substrate of a first conduction type, a double heterostructure including a clad layer of the first conduction type, a light absorbing layer and a clad layer of a second conduction type successively formed in an opening of the oxide film, and an embedding structure for covering over the entire double heterostructure. The optical modulator is characterized in that the carrier concentration of the clad layer of the first conduction type exhibits a continuous variation from the semiconductor substrate to the light absorbing layer or the carrier concentration of the embedding structure portion exhibits a variation from a low concentration to a high concentration.

Abstract: An electro-optical modulator has an electro-optical crystal having an optical path, and a pair of electrodes disposed one on each side of the optical path for applying a signal voltage therebetween. At least one of the electrodes is formed on a side surface of a groove defined along the optical path of the electro-optical crystal.

Abstract: A polarization plane switch comprising a Faraday rotator made of an iron-containing garnet single-crystal film and magnetic field applying devices capable of reversing a magnetic field to be applied to the Faraday rotator. The polarization plane switch has a structure in which magnetization of part of the Faraday rotator is unsaturated and that of the remaining portion of it is saturated when a magnetic field is applied to the Faraday rotator by the magnetic field applying device, and a light beam passes through the magnetically saturated portion almost vertically to the film surface. As the above Faraday rotator, it is the most preferable to use a Faraday rotator made of Bi-substituted iron garnet single crystal formed by liquid-phase epitaxy and having a compensation temperature, and thermally treated under the top condition at a temperature between 1,120.degree. and 1,180.degree. C. for 7 hours or less.