Abstract: A multi-channel receiver which exploites the parallel processing advantages of an optical signal processor is used to facilitate 100 percent intercept of an incomming RF signal in a dense RF environment. The receiver performs real time parallel signal processing to effectively capture a given signal of interest. The receiver modulates a laser beam with incoming RF signals. The modulated laser beam is then Fourier transformed, channelized into an array of signals of varying frequencies, optically filtered and then down converted into their original radio frequencies with only the pass characteristics altered so that the captured signal can be readily identified. An electronic controller is used to control the pass structure of the optical filter which can be reconfigured in real time to selectively pass signals having the desired characteristics.

Abstract: A 3-channel modulation system for a high power laser and a modulation method for a high power laser are disclosed herein. In a preferred implementation, the modulation system includes a laser light source, a light modulator modulating the light generated from the laser light source and including a pair of electrodes having a predetermined area disposed on one side of the light modulator, an image signal generating sub-system, a drive circuit sub-system for operating the electrodes so that the image signal being generated from the image signal generating sub-system is provided through the electrodes to the light modulator, a first cylindrical lens positioned between the laser light source and the light modulator so that the area and form of the light generated from the laser light source are modified and the modified light enters the light modulator, and a second cylindrical lens positioned at an output side of the light modulator to modify the area and form of the light modulated by the light modulator.

Abstract: An acousto-optic modulator comprised of an acousto-optic element coated with an anti-reflection layer, and a method of manufacturing the same, are provided. The acousto-optic modulator includes an anti-reflection layer, comprised of at least two coating layers having different refractive indices, formed on the light incident/emitting surface of an ultrasonic medium for modulating a light beam incident from an optical source.

Abstract: An electronically agile spectro-polarimetric imager is described in which an acousto-optic tunable spectral filter (AOTF) is located in series with an electronically tunable optical phase modulation plate such that incident radiation will pass through the modulation plate and the AOTF in sequence. This system makes it possible to perform both spectral analysis, complex polarization analysis and object discrimination at video-rates of incident radiation from complex target scenes according to the spectral content and polarization state of the radiation reflected or emitted from the objects within the scene, regardless of the polarization state of the incident radiation. Embodiments for analyzing incident radiation of various wavelengths are provided.

Abstract: Cathode electrodes in a plurality of rows are arranged parallel with one another on a glass substrate. Very small cold cathodes of conical shape are arranged in matrix on the cathode electrodes. An insulating layer (ITO film) having cylindrical slots surrounding cold cathodes is formed above the glass substrate and the cathode electrodes. Gate electrodes in a plurality of columns are formed on the insulating layer in the direction perpendicular to the extension of the cathode electrodes. An intersection between a cathode electrode and a gate electrode corresponds to a pixel. A glass plate is provided above the gate electrodes. An anode electrode is provided entirely on the surface of the glass plate facing the cold cathodes. A phosphor member for each pixel is formed on the surface of the anode electrode facing the cold cathodes. Thus, the light source for emitting light for each pixel is formed.

Abstract: A polarization independent acousto-optic tunable filter (PIAOTF) used for multiwavelength switching and routing in wavelength division multiplexing (WDM) networks. In the PIAOTF an incident unpolarized light beam is divided to propagate and to be diffracted along two polarization division branches. By using polarization converters and equal optical paths for the two polarization division channels, a PIAOTF is created which minimizes polarization dependent loss and polarization mode dispersion. Furthermore, a preferred embodiment of the AOTF using an elongated acousto-optic interaction medium is described that provides the additional advantages of narrow bandwidth, lower drive power and easier alignment.

Abstract: In a non-collinear type acousto-optic tunable filter, the incident angle of a source light beam L.sub.1 radiated from a light source 6 onto an acoustic medium 1 is set at an equivalence incident angle for which the wavelength .lambda..sub.i of the diffracted ordinary ray L.sub.3 and the wavelength .lambda..sub.i ' of the diffracted extraordinary ray L.sub.4 become approximately identical. Further, the diffracted ordinary ray L.sub.3 and the diffracted extraordinary ray L.sub.4 of the approximately identical wavelength are superposed, and the intensity of the superposed ray is detected. Consequently, spectrometry is performed based on the superposed diffracted ray having twice the intensity and a very sharp waveform, so that accurate spectroscopy can be made possible even if the intensity of the source light beam is low.

Abstract: An acousto-optic tunable filter and filtering method are disclosed providing for a significantly increased number of available wavelength channels for output. The filter combines a diffraction grating, the grating vector of which is transverse to light propagation direction, with an acousto-optic beam deflector, which, by accommodating a narrow spectral bandwidth (about 5% that of conventional acousto-optic tunable filters), provides significantly increased output bandwidth and available wavelength channels (by a factor of approximately 20).

Abstract: An acousto-optic tunable filter based on isotropic acousto-optic diffraction using phased array transducers. The isotropic AOTF provides the advantages of narrow optical passband, low acoustic frequencies, and insensitivity to the input optical polarization. Preferred embodiments of the isotropic AOTFs are described for optimized spectral resolution and diffraction efficiency.

Abstract: A light microscope comprises a light source and a first acousto-optic tunable filter responsive to the light source for producing two light streams of different polarization. A control circuit is provided for tuning the first filter to a plurality of frequencies. A mechanism, such as steering optics, is provided for combining the two light streams into a combined light stream. Input optics focus the combined light stream. A condenser, such as a darkfield condenser, receives the focused, combined, light stream and projects it onto a sample. A second acousto-optic tunable filter is responsive to light from the sample. A second control circuit is provided for tuning the second acousto-optic filter to a plurality of frequencies. The light from the second acousto-optic tunable filter may be captured and stored for future processing.

Abstract: Disclosed is a high-speed frequency modulation signal source which has a voltage-controlled oscillator to which a voltage is input to change an oscillation frequency; and a frequency down converter in which a frequency output from the voltage-controlled oscillator is converted into a desired frequency. Also disclosed is a high-speed variable optical wavelength filter which has the above high-speed frequency modulation signal source; a band-pass filter in which a frequency component is extracted from the desired frequency output from the high-speed frequency modulation signal source; and an acousto-optic filter which is driven by the frequency component output from the band-pass filter.

Abstract: An imaging system comprises an acousto-optic tunable filter for receiving light at an input end thereof and outputting light at an output end thereof. A control circuit is provided for tuning the filter. A prism is responsive to the light output by the tunable filter. The prism is oriented at an angle with respect to the filter to compensate for dispersion of the output light caused by the tunable filter.

Abstract: Combining a tristimulus filter, two lenses, and a crystalline colloidal ay filter in an arrangement resulting in a visible optical limiter without substantial color distortion that can be used for eye or sensor protection. Only three nonlinear colloidal arrays are needed to Bragg reflect over the pass bands of the tristimulus filter. The nonlinear colloidal array is arranged so that the band reflected (at the least) completely overlaps the pass band of the tristimulus filter.

Abstract: In a variable wavelength optical filter, a lens (3) is positioned at the output end of a first optical fiber (1) and transforms an input optical signal to parallel light. A dielectric interference optical filter (8) is located at the rear of the lens (3) in order to transmit only the light of particular wavelength. A lens (4) converges the light output from the filter (8) into the input end of a second optical fiber (2). A rotary plate (7) is affixed to the output shaft (6) of a servo motor (5) whose rotation angle is controlled by an electric signal fed from the outside of the filter. The filter (8) is mounted on the rotary plate (7) with the intermediary of a piezoelectric element or elements (9). The piezoelectric elements (9) are caused to oscillate by a modulating signal, so that the transmission center wavelength of the filter is varied. The resulting deviation of the transmission center frequency is detected.

Abstract: A light modulator having the small volume and low power consumption of LCD displays together with the higher resolution and faster response time of CRT displays. The light modulator includes a substrate pair, an opaque light shielding layer, a shutter assembly composed of a shutter plate and a shutter suspension, and electrodes. The substrate pair includes a first substrate and a second substrate positioned parallel to each other and spaced from one another to define a cavity. The opaque light shielding layer is located on one of the substrates, and defines a translucent window. The shutter assembly is located in the cavity. The shutter plate is movably mounted adjacent the window by the shutter suspension. The shutter suspension includes elastic support members disposed between the shutter plate and the substrate pair.

Abstract: In an acousto-optic filter, a channel type optical waveguide is fabricated on a substrate. First and second surface acoustic wave transducers are mounted on the optical waveguide, respectively, in correspondence with input and output terminals thereof to transduce first and second surface acoustic waves. First and second polarization converters respectively convert only a specific wavelength component of first linearly polarized light excited at the input terminal of the optical waveguide through interaction of the first surface acoustic wave into second linearly polarized light perpendicular to the first linearly polarized light, and only a specific wavelength component of second linearly polarized light obtained by conversion of the first polarization converter through interaction of the second surface acoustic wave generated by the second surface acoustic wave transducer into first linearly polarized light.

Abstract: An apparatus for, and method of, decreasing a temporal duration of an optical input pulse having an input power spectrum associated therewith, the apparatus and method operative on at least unchirped optical input pulses. The apparatus comprises: (1) a zero-dispersion pulse shaper for receiving the optical input pulse and spectrally spreading the input pulse to produce a spectrally-spread pulse and (2) a modulator array interposed within the zero-dispersion pulse shaper for receiving the spectrally-spread pulse and selectively attenuating a portion of the power spectrum of the spectrally-spread pulse by a predetermined amount to produce a selectively-attenuated spectrally-spread pulse, the zero-dispersion pulse shaper focusing and recombining the selectively-attenuated spectrally-spread pulse to produce an output pulse having a broader power spectrum than the input pulse, the output pulse further having a temporal duration less than the input pulse, regardless of whether the input pulse is chirped.

Abstract: A high definition image projector is provided for modulating light using an acousto-optic tunable filter according to image signals and projecting the modulated light on a screen. An image is obtained by modulating a light beam by pixel units according to the image to be displayed and directly projecting the modulated light beam on the screen in corresponding pixel units. High quality images can thus be displayed on a large screen. By adopting a high-output light source, a high luminance image can be obtained.

Abstract: A method and device for shaping both the temporal and spatial profiles of an input optical pulse to generate an output optical waveform are described. The method includes the step of dispersing the spectral frequencies of the input pulse. These frequencies are then focused with a cylindrical lens to form a two-dimensional optical field. The field is imaged on a mask featuring a two-dimensional array of pixels. The amplitudes, phases, or phases and amplitudes of the two-dimensional optical field are then filtered with the mask. The filtered spectral frequencies are then recombined to form the collective temporal profile of the output waveform. The two-dimensional optical field is then imaged in a sample plane to form the spatially coherent regions.

Abstract: An acousto-optical filter (AOTF) having reduced sidelobes. The AOTF is fabricated with a waveguide formed on a substrate along an optical axis. An incoming beam of light is coupled into the waveguide. An acoustic wave beam is induced by an interdigitated transducer. The acoustic wave beam follows an acoustic wave beam axis which crosses the optical axis. The transducer is driven by an externally-generated electric signal. The frequency of the acoustic wave beam is determined by the frequency of the electric signal. The acoustic wave beam induces a diffraction grating in the waveguide as the acoustic wave beam crosses the optical axis, and this in turn diffracts the beam of light. The grating couples the transverse electric and transverse magnetic polarization modes of the light, but only within a narrow band of optical wavelengths. The cross-section of the intensity of the acoustic wave beam can be tapered to further reduce the sidelobes of the passband defined by the frequency of surface acoustic wave beam.

Abstract: Modulated interference effects arising when laser beams are modulated by photoelastic modulators are substantially eliminated by methods and apparatus that extract from the detected beam the modulated, interfering light that emanates from the optical element of the modulator.

Abstract: An apparatus for both deflecting a beam of light illuminating a spot on a surface and varying the size of the spot, electronically, without changing any system components. The apparatus includes an acousto-optic deflector driven with a linear FM signal produced by a chirp signal generator. The linear FM signal is characterized with a dispersion rate, and the chirp signal generator includes a chirp dispersion selector to vary the dispersion rate. A beam of collimated light passes through the acousto-optic deflector and appropriate focusing optics image the beam onto a spot in a nominal focal plane. The chirp dispersion selector sets the dispersion rate in accord to a nominal rate, resulting in the beam illuminating a spot in the focal plane. Generally, the focal plane coincides with a wafer surface, of the type having periodic and non-periodic features on it. The spot size may be varied from that of a diffraction limited spot to a spot whose maximum size is system dependent.

Abstract: A signal filter, and method of signal filtering, in which an optical signal s spatially dispersed according to frequency, and undesired frequencies blocked out. In an embodiment, a Bragg cell receives a (typically microwave) signal, and transduces it to an acoustic signal. A light source, e.g. a laser diode, directs light through the acoustic signal in a known manner so as to produce an optical output which is spatially dispersed according to frequency. A programmable spatial light modulator blocks out unwanted frequency components. Upon removal of the optical carrier, e.g. by heterodyning the spatial light modulator's output with a reference signal from the light source, the components can be recombined into a resultant filtered signal. The invention can be used as a repeater, a military electronic countermeasure, in environments which have large amounts of electromagnetic clutter but in which one does not want the clutter repeated.

Abstract: Acousto-optical devices utilize crystals of a novel material thallium arsenic sulfide (Tl.sub.3 AsS.sub.3) grown from a melt. A Tl.sub.3 AsS.sub.3 crystal is cut and parallel faces are prepared and polished. A piezoelectric transducer connected to an RF generator is placed on the acoustic face to generate sound waves. The light is directed through the optical face of the crystal and interacts with the acoustic waves. These devices may be used in signal processing, spectrum analyzing, spectroscopic, liquid analyzing and spectral imaging systems.

Abstract: A passive broadband sensor protection and enhancement system and technique. ncident light is focused with a cylindrical lens on the optical axis into an intense light strip onto the input face of a photorefractive crystal which may include optional anti-reflection coatings on the input and output face. A broadband high reflection coating proximate to the input face reflects all radiation from approximately 0.68 out to at least 1.5 micrometers wavelength and light exiting includes a transmitted beam and beam fan. A weak holographic grating is used to seed the beam fan, such that is fanned out of the optical path in a direction determined by the c-axis, dominant electro-optic coefficient, and charge carriers participating in the photorefractive process. The transmitted beam contains only incoherent radiation as input to a sensitive detector resulting in broadband multiline protection from the visible spectrum for substantially all pulsewidths and cw lasers, with enhanced time response and interaction length.

Abstract: An acousto-optic polychromatic light modulating apparatus employs an acousto-optic medium, and a single piezoelectric transducer, which is driven by a plurality of frequency components, the intensities of which are controlled in response to input electronic data, to produce a color-modulated diffracted polychromatic output beam. The acousto-optic medium and mode as well as acousto-optic interaction length and the geometry of the device are selected such that there is negligible acousto-optic interaction with a given frequency signal on all output optical beam colors except for the one assigned to that frequency, with a high degree of color convergence achieved over a wide wavelength range. The present invention can be used to increase the modulation rate of a polychromatic modulator by selecting the incident optical beam energy propagation direction to be nearly normal to the acoustic wave phase propagation direction with non-parallel tangents at the incident and diffracted optical wave-vector loci.

Abstract: Acousto-optic polarization converters can be used as the primary optical components in a multi-channel wavelength-routing switch (101). Switching efficiency is decreased and the polarization converted wavelength channels are shifted towards each other, however, when closely neighboring channels are selected simultaneously. This degradation has serious consequences for many applications of the acousto-optic polarization converter. By applying counterpropagating acoustic waves from opposite ends of a converter (400) and using an acoustic absorber (417) to separate the left and right sides of the converter at a defined coupler crossover length, L.sub.x, this deleterious degradation is substantially reduced.

Abstract: An acousto-optic tunable filter ("AOTF") with a pair of electrodes on opposite sides of the waveguide. A voltage source applies a potential across the electrodes, thereby creating an electric field through the waveguide. The electric field controls an optical property of the waveguide by altering the birefringence of the waveguide. Suitably adjusting the potential applied by the voltage source results in suppression of sidelobes, correction of asymmetric sidelobes, and compensation for physical variations in the waveguide. The AOTF can be tuned very rapidly by a tuning voltage applied to the electrodes. In combination with a thermistor, the control voltage can compensate for changes in temperature. A spatially-varying electric field is generated by using a set of electrodes at different potentials, or by using a resistive element as an electrode, or by shaping the electrodes according to the desired field. A rapidly-varying control voltage can modulate a light beam in the filter.

Abstract: A wavelength-selective arrangement interacts with optical radiation propagating in a transmission medium. The arrangement includes a selector member made of a polar organic material which exhibits piezoelectric properties, the selector member having an interaction surface for interacting with the radiation. The selector member is provided with structure for propagating surface acoustic waves along the interaction surface so as to create a grating and thereby determine its interacting properties in relation to the wavelength of the radiation, in a selectively variable manner.

Abstract: An acousto-optic tunable filter (100) is provided with an acousto-optic interaction profile that results in a frequency response with near-ideal bandpass filter characteristics of near-unity transmission inside the passband and near-zero transmission outside the passband. The acousto-optic interaction profile which results in this frequency response has a phase polarity which alternates and is damped, i.e. the acousto-optic interaction profile has a damped oscillating shape. The physical structure to implement this filter comprises a pair of acoustical waveguides (110, 112) which taper toward each other at the beginning of the profile and then are spaced apart by a constant distance. A damping layer (132) or other damping structure is provided to achieve the damping characteristics of the profile.

Abstract: An electronically tunable optical filter utilizing noncollinear acousto-optic interaction in an acoustically anisotropic, optically birefringent crystal. The directions of optical and acoustic waves are chosen so that the optical ray is collinear with the group velocity of the acoustic wave. The collinear beam configuration provides increased spectral resolution and reduced drive power.

Abstract: The optical device can examine a spectrum at low resolution and subsequently choose a portion of that spectrum to be examined at higher resolution, using a single detector array for both spectra. The latter spectrum can be chosen to be arbitrarily anywhere within the low resolution spectrum. The device comprises a source of input light, a wedged shaped dispersive device, a first reflective mirror, a second reflective mirror, a RF generator connected to the dispersive device, and a detector array. In operation, the dispersive device provides a low dispersion spectrum in the zero order light when the source of light is impinged upon it. When the RF generator is turned on, a second spectrum which is diffracted is obtained. This will be the high resolution spectrum. By operating near 100% diffraction efficiency, it is possible to switch from one spectrum to the other. By adjusting the RF frequency the band center of the high resolution spectrum can be varied to fall anywhere within the low resolution spectrum.

Abstract: An acousto-optic apparatus is described that varies the time delay of electrical signals over a continuum of delays. In the preferred embodiment, a light source, which can be either coherent or incoherent, emits an optical beam that is focused into an acousto-optic cell. An input electrical signal is used to drive the acousto-optic cell which, in turn, modulates the focused optical beam. Portions of the input optical beam are modulated and diffracted at angles proportional to the frequencies and phases contained in the input electrical signal. By appropriately choosing the cone of angles at which the light is focused into the acousto-optic cell, the diffracted optical beam can be made to overlap with portions of the undiffracted, unmodulated optical beam. All of the light exiting the acousto-optic cell is then collected onto a device for detection. Optical photomixing of the diffracted beam and the undiffracted beam is performed in order to derive the input electrical signal with a time delay.

Abstract: An improved AOTF-based imaging spectrometer that has ability to electronically set the bandpass wavelength of an AOTF to any desired value in its wide tuning range, provides significant observational flexibility. This allows observations to be tailored in real-time and enables the spectrometer to address a wide range of objectives and permits real-time modification of the observational parameters, such as in flight or in other situations in which only remote control is possible. Various improvements in optical architecture provide simplified magnification variability, improved image resolution and light throughput efficiency and reduced sensitivity to ambient light. A preferred embodiment employs a camera zoom lens as the input lens. A TeO.sub.2 AOTF and a relay lens are placed at selected distances behind the back focal plane of the input lens, respectively.

Abstract: Apparatus is described for achieving wavelength selection. Furthermore, the apparatus exhibits very high wavelength resolution, stable operation and rapid returning. A bundle of multi-wavelength light, entering the device, is acoustooptically deflected. This is done by driving two orthogonal acoustic transducrs of the deflector with two suitable frequencies fx and fy. The light so deflected passes first through a wedge etalon having a taper along the X-axis and then through a second wedge etalon having a taper along the Y-axis. The pair of wedges forms two, single-cavity etalons. Depending on the choice of fx and fy, any wavelength within the wavelength range covered by the two, single-cavity etalons can be selected rapidly and accurately.