Abstract: A method and apparatus for a photoinduced electromotive force sensor. The sensor has an active substrate formed of a semi-insulating photoconductor with sufficient carrier trap density to form an effective charge grating and pairs of electrodes disposed on the active substrate, where the sensor is configured to reduce the photovoltaic effect caused by the incident light in the vicinity of the electrodes. The shape or composition of the electrodes may be selected to reduce the photovoltaic effect or the electrodes may be disposed on the substrate to average out the photovoltaic effect arising from each one of the electrodes.

Abstract: A method and apparatus for a photoinduced electromotive force sensor. The sensor has an active substrate formed of a semi-insulating photoconductor with sufficient carrier trap density to form an effective charge grating and pairs of electrodes disposed on the active substrate, where the sensor is configured to reduce the photovoltaic effect caused by the incident light in the vicinity of the electrodes. The shape or composition of the electrodes may be selected to reduce the photovoltaic effect or the electrodes may be disposed on the substrate to average out the photovoltaic effect arising from each one of the electrodes.

Abstract: An optical frequency modulated transmitter includes a plurality of separately phased-controlled slave lasers, the outputs of which are combined to form a single output beam of the transmitter. A master optical oscillator outputs an optical signal for injection locking the plurality of slave lasers, the optical signal being frequency modulated directly in the master optical oscillator or externally thereof. Additionally, a method of frequency modulating an optical beam is disclosed using a plurality of slave lasers. Each of the slave lasers has an output, the outputs of which are combined to form the optical beam. The plurality of slave lasers is injection locked to an optical output of a master oscillator. The optical output of the master oscillator is frequency modulated before the optical output is applied to the plurality of lasers. Each slave laser of the plurality is phased controlled relative to other slave lasers of the plurality.

Abstract: A photo-EMF detector including a shield to prevent a portion of the detector from illumination. The shield prevents the generation of unwanted noise-currents, thus increasing the performance of the photo-EMF detector.

Abstract: A system and a method for remotely sensing global motion of an ensemble of dynamically moving scattering sites. The system comprising a scattering medium under inspection, an optical transceiver and a detector in a double-pass geometry.

Abstract: A remote mass is excited with one or more beams, and the surface vibrations of the excited mass are detected with one or more laser vibrometers. Each vibrometer generates a signal indicative of the surface vibrations which is stored, reversed in time, and applied to modulate an exciter beam that is then impinged onto the mass.

Abstract: A remote mass is excited by a plurality of beams generated sequentially by each one of a plurality of time reversal mirrors, and the surface vibrations of the excited mass are detected by a laser vibrometer in each of the time reversal mirrors. Each vibrometer generates a signal indicative of the surface vibrations which is stored, reversed in time, and applied to modulate the exciter beam impinged onto the mass by the respective time reversal mirror.

Abstract: An optical apparatus for coherent detection of an input optical beam. The apparatus includes a beam splitter for splitting the input optical beam into a first component and a second component; an optical delay device arranged to receive the second component, the optical delay device imposing an intentional delay in the second component of the input optical beam; and an adaptive beam combiner coupled to receive the second component with a delay imposed thereon by the optical delay device; and the first component from the beam splitter. The adaptive beam combiner has two exiting components having the same wavefronts and propagating directions as the first and second components and being in quadrature. A detector arrangement is provided for receiving and detecting the first and second exiting components from the adaptive beam combiner.

Abstract: A photo-EMF sensor and a method of making same has a substrate with a semiconducting layer; a plurality of sensing regions in the layer, each sensing region including (i) a pair of electrodes disposed in, on or above the layer and (ii) an active region in the layer disposed adjacent said pair of electrodes; and a plurality of inactive regions in said the arranged between adjacent sensing regions. The inactive regions and the sensing regions are dosed with a desensitizing agent, the inactive regions receiving a relatively higher dose of the desensitizing agent and the sensing regions receiving a relatively lower dose of the desensitizing agent. The active layer is preferably placed in a monolithic Fabry-Perot cavity to enhance the optical efficiency and performance of the sensor.

Abstract: An excitation signal is selected and transmitted, and a signal is received containing information produced by a remote object in response to the excitation signal. The information is evaluated to attempt to identify the object, the excitation signal is adjusted on the basis of the evaluation, the adjusted excitation signal is transmitted, and a resulting signal is received and evaluated. A variation involves transmitting an excitation signal, transmitting an optical probe signal, receiving an optical signal which is a reflection of the probe signal and which contains information produced by a remote object in response to the excitation signal, and evaluating the information for the purpose of identifying the object.

Abstract: An inter vehicle communication system wherein information transfer between vehicles is provided by data sources, data sensors, and vehicle sensors on each vehicle connected to a central processing unit on each vehicle. The central processing unit receives information from other vehicles via the data sensors and calculates information weights for that data. Information weights may be based upon temporal or spatial displacement, or other factors. The central processing unit then combines that weighted data with data provided by onboard vehicle sensors to determine vehicle and situational status. The central processing unit will then provide control information to the vehicle or vehicle operator. The central processing unit also creates messages for transfer to other vehicles via the data sources contained in the vehicle. Preferably, the data sources are provided by adapting vehicle headlights, taillights, or other existing lights sources for optical data transfer.

Abstract: An optical frequency modulated transmitter includes a plurality of separately phased-controlled slave lasers, the outputs of which are combined to form a single output beam of the transmitter. A master optical oscillator outputs an optical signal for injection locking the plurality of slave lasers, the optical signal being frequency modulated directly in the master optical oscillator or externally thereof. Additionally, a method of frequency modulating an optical beam is disclosed using a plurality of slave lasers. Each of the slave lasers has an output, the outputs of which are combined to form the optical beam. The plurality of slave lasers is injection locked to an optical output of a master oscillator. The optical output of the master oscillator is frequency modulated before the optical output is applied to the plurality of lasers. Each slave laser of the plurality is phased controlled relative to other slave lasers of the plurality.

Abstract: A vibrometer for probing an object to determine its vibratory signature and a method of probing same. The vibrometer includes a laser for generating a laser beam for probing the object; a detector for detecting reflections from the object; and a two beam input phase-conjugate mirror located so as to receive a portion of the laser beam produced by the laser and a portion of the laser beam reflected from the object, the two input beam phase-conjugate mirror reflecting received diffuse signals from the object back towards the object.

Abstract: A vibrometer for probing an object to determine its vibratory signature and a method of probing same. The vibrometer includes a laser for generating a laser beam for probing the object; a detector for detecting reflections from the object; and a two beam input phase-conjugate mirror located so as to receive a portion of the laser beam produced by the laser and a portion of the laser beam reflected from the object, the two input beam phase-conjugate mirror reflecting received diffuse signals from the object back towards the object.

Abstract: A photo-EMF sensor and a method of making same has a substrate with a semiconducting layer; a plurality of sensing regions in the layer, each sensing region including (i) a pair of electrodes disposed in, on or above the layer and (ii) an active region in the layer disposed adjacent said pair of electrodes; and a plurality of inactive regions in said the arranged between adjacent sensing regions. The inactive regions and the sensing regions are dosed with a desensitizing agent, the inactive regions receiving a relatively higher dose of the desensitizing agent and the sensing regions receiving a relatively lower dose of the desensitizing agent. The active layer is preferably placed in a monolithic Fabry-Perot cavity to enhance the optical efficiency and performance of the sensor.

Abstract: An optical apparatus for coherent detection of an input optical beam. The apparatus includes a beam splitter for splitting the input optical beam into a first component and a second component; an optical delay device arranged to receive the second component, the optical delay device imposing an intentional delay in the second component of the input optical beam; and an adaptive beam combiner coupled to receive the second component with a delay imposed thereon by the optical delay device; and the first component from the beam splitter. The adaptive beam combiner has two exiting components: a first exiting component being representative of the difference of the first and second components received thereby and a second exiting component being representative of the sum of the first and second components received thereby. A detector arrangement is provided for receiving and detecting the first and second exiting components from the adaptive beam combiner.

Abstract: A dual time delay interferometer (TDI) enables remote sensing of phase modulated information, such as the detection of ultrasonic vibrations from highly diffuse surfaces, preferably in the range from about 10 kHz to 100 MHZ or more. The system can also be configured in a transceive mode with a dual pass through a single TDI, which is well suited to optical communications. A non-steady-state photo-electromotive-force detector tracks the movement of interference fringes (whose position shifts as the surface vibrates), rather than their absolute position. A phased array of the sensors can be used for enhanced imaging applications requiring better signal/noise ratios, or alternatively, when lower power optical sources are employed.

Abstract: An ultrasound detection system that is relatively insensitive to rough workpiece surfaces, suppresses low frequency noise, and provides high sensitivity without the need for active stabilization. An optical probe beam is reflected and phase modulated by a workpiece surface that is being vibrated by ultrasound. A time-delay interferometer optically interferes the phase modulated probe beam with a time-delayed replica of itself. The optical interference generates optical interference fringes that move in accordance with the workpiece surface velocity. The interference fringes are detected by a non-steady-state photo-electromotive-force (NSS-photo-EMF) detector that generates an output signal when the frequency of fringe motion exceeds a predetermined threshold.

Abstract: A laser-ultrasonic inspection system is provided for on-line and off-line inspection of a workpiece. The system utilizes an optical acoustic wave generation and detection system with relatively high spatial resolution and which appreciably reduces the effects of parasitic acoustic coupling. An array of acoustic waves are generated in the workpiece by a short pulse optical transmitter bee with a beam geometry that is tailored to focus the acoustic waves at an inspection site in the workpiece. The acoustic waves that probe the inspection site are then detected by reflecting an optical read-out beam from a surface of the workpiece and optically interfering it with an optical reference beam. The geometry of the optical read-out beam is chosen such that the read-out beam only detects the acoustic waves that arrive from the inspection site (acoustic waves that arrive from other parasitic acoustic sources are out of phase with respect to each other and cancel out).

Abstract: A low noise system and method for both amplifying and retroreflecting an information-bearing probe beam employs a two-wave mixer in conjunction with a pseudoconjugating element. The probe beam is amplified by two-wave mixing in a photorefractive medium, while the pseudoconjugator is arranged to retroreflect the amplified probe beam back through the photorefractive medium such that optical distortions imposed upon the beam during the amplifying pass are compensated, yielding an output with a high signal-to-noise ratio. Various types of pseudoconjugating elements may be used.