Abstract: Methods and apparatus directed to using modulation to substantially improve detection limits in optical imaging, and to substantially improve the performance of various optical imaging systems. In an illustrative embodiment, such modulation is achieved using a modulated light source, a modulation frequency reference, a detector, and a demodulator. The modulated light source may comprise a light source emitting an inherently modulated output; alternately, this modulated light source may comprise a separate optical modulator and a continuous wave, modulated, or pulsed light source configured so as to impose a modulation in the output of light source. Methods for imagine using such modulation are also disclosed.

Abstract: A method and apparatus for modulating light, wherein a light source provides light of a certain wavelength to be modulated by a layer of superconducting material which forms part of a specifically configured plate assembly. The superconducting layer is placed in the optical path of the light source. Further the superconducting layer is switched between a partially transparent non-superconducting state and a substantially non-transparent superconducting state by a modulation circuit. The resulting optical pulses transmitted through the superconducting layer are converted from the original wavelength to a lower wavelength by a frequency converting device.

Abstract: A first optical modulator converts an electrical signal into an optical-frequency-modulated signal, supplying the same with unmodulated light from a local light source to a first optical receiver. The first optical receiver generates an FM signal, which is a beat signal between the received two lights. This, FM signal is supplied to a filter, where only the carrier component thereof is extracted, and the carrier component is converted in frequency in the frequency converter. With the resultant signal after frequency conversion, a second optical modulator optically modulates the amplitude or intensity of the unmodulated light from the local light source. A second optical receiver receives the resultant signal after optical modulation and an optical signal from the first optical modulator, producing an FM signal, which is a beat signal between the received two optical signals.

Abstract: A method and apparatus accommodate for wavelength drift of optical sources. The apparatus includes an optical source having a wavelength control port and an output port, providing one or more optical signals that drift at a first rate. A signal generator within the apparatus provides a control signal to the wavelength control port of the optical source that causes wavelength variations to be superimposed on the wavelength drift of the one or more optical signals. The superimposed wavelength variations occur at a second rate that exceeds the first rate. The apparatus also includes a receiver coupled to the output port of the optical source, that receives the one or more optical signals having the superimposed wavelength variations. The receiver accommodates for the wavelength variations caused by the control signal, enabling a received wavelength to be distinguished from the drifting wavelength of the optical source. A corresponding method accommodates for wavelength drift of optical sources.

Abstract: The present invention relates to an interferometer useful in the interleaving and de-interleaving of optical wavelength channels. Typically the invention comprises a beamsplitter and two resonators, e.g. GT etalons or ring resonators. The beamsplitter splits an input beam of light into a first sub-beam directed to follow a first path and a second sub-beam directed to follow a second path. The first resonator has a first effective cavity length and receives the first sub-beam. The second resonator has a second effective cavity length and receives the second sub-beam. The first path and the second path have an effective optical path difference approximately equal to one-half the first effective cavity length. In one embodiment, the front plates of the GT etalons each have a different reflectivity, and are selected to provide a desired spectral response.

Abstract: An optical communication system (10), a method (100) for parallel modulation of an optical spectrum and a method (200) for parallel demodulation of the optical spectrum of modulated optical frequencies by the system (10) are described. The optical frequencies are provided in parallel to a modulation section (14) for modulating with data bits from a data signal source (16). The data bits are associated with an optical modulator (58) that controls passage of the optical spectrum at a plurality of predetermined optical frequencies based upon the data bits. The optical frequencies of the optical spectrum, modulated by the data bits, are then transmitted via a communication section (18) to an optical receiver (20) that is coupled to a demodulation section (22) of the system (10). Modulated optical frequencies are received as a modulated optical spectrum and demodulated in parallel by an optical demodulator (92) to derive the data bits.

Abstract: A demodulation system used in connection with an analog optical link. An optical carrier signal modulated with an RF signal is split into two portions. One carrier signal portion is applied to a coarse demodulator that generates a demodulated signal representative of the RF signal and the additive inverse of an error signal. The coarse demodulator output is inverted and applied to a phase modulator along with the second carder signal portion. The phase modulator modulates the optical carrier signal with the additive inverse of the demodulated signal from the coarse demodulator, and the RF signal components of the carrier signal and the demodulated signal cancel, leaving the carrier signal modulated with the error signal. The modulated carrier signal is filtered, then demodulated to regenerate the error signal, which is combined with the demodulated signal from the coarse demodulator to recreate the RF signal with minimal excess noise and distortion.

Abstract: Methods and apparatus directed to using modulation to substantially improve detection limits in optical imaging, and to substantially improve the performance of various optical imaging systems. In an illustrative embodiment, such modulation is achieved using a modulated light source, a modulation frequency reference, a detector, and a demodulator. The modulated light source may comprise a light source emitting an inherently modulated output: alternately, this modulated light source may comprise a separate optical modulator and a continuous wave, modulated, or pulsed light source configured so as to impose a modulation in the output of light source. Methods for imaging using such modulation are also disclosed.

Abstract: A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source (12) for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle.

Abstract: A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source (12) for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle.

Abstract: The optical assembly for modulating input light and providing modulated light at an output thereof includes a first arrangement, which includes a layer of a superconductive material having at least a part of the input light incident thereon as incident light. The superconductive material is switchable between a first state, in which the superconductive material exhibits a first refractive index, and a second state, in which the superconductive material exhibits a second refractive index. The first arrangement is configured to direct to the output as the modulated light a first fraction of the incident light, when the superconductive material is in the first state, and a second fraction of the incident light, when the superconductive material is in the second state, such that the modulated light exhibits a given value of extinction ratio, which is defined as a ratio of the first fraction of the incident light to the second fraction of the incident light at the output.

Abstract: An optical modulation scheme for transmitting data over a fiber optic transmission line is proposed where the following steps are realized:

Abstract: Methods and apparatus directed to using modulation to substantially improve detection limits in optical imaging, and to substantially improve the performance of various optical imaging systems. In an illustrative embodiment, such modulation is achieved using a modulated light source, a modulation frequency reference, a detector, and a demodulator. The modulated light source may comprise a light source emitting an inherently modulated output; alternately, this modulated light source may comprise a separate optical modulator and a continuous wave, modulated, or pulsed light source configured so as to impose a modulation in the output of light source. Methods for imaging using such modulation are also disclosed.

Abstract: The present invention discloses an electronically frequency tunable and phase modulatable quasi-optic grid oscillator. The oscillator includes a reference signal input port whereby a small external reference signal is introduced that entrains the frequency and phase of the oscillator signal to it. Amplitude modulation techniques are introduced to further enhance the utility of the oscillator as a modulator.

Abstract: With respect to the relative intensity noise (RIN) for inputs to an optical modulator or the signal-to-noise ratio (SNR) for outputs therefrom, the optical modulator modulating coherent lights of different wavelengths obtained by slicing a spectrum of the multi-wavelength light, the shape of a spectrum of a multi-wavelength light is controlled so that predetermined RIN and SNR can be obtained in accordance with transmission system parameters (the type and distance of optical fibers, the number of repeaters), thus enabling design meeting a performance specification for a conventional transmission section using semiconductor lasers.

Abstract: An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed. The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics. In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens. A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay. This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror. In other embodiments, this device permits optical delay scanning without the use of moving parts.

Abstract: A spatial frequency converting device in which the amount of conversion of spatial frequency characteristics is variable. An optical system using the spatial frequency converting device is a variable-focus optical system in which the depth of field can be enlarged by fixed signal processing. A pupil modulation element provided in a fixed-focus optical system includes a plurality of elements. At least one of the elements is rotated about an optical axis. In the variable-focus optical system, a movable lens placed on the object side of a pupil modulation element is moved along an optical axis.

Abstract: A method and apparatus for modulating light, wherein a light source provides light of a certain wavelength to be modulated by a layer of superconducting material which forms part of a specifically configured plate assembly. The superconducting layer is placed in the optical path of the light source. Further the superconducting layer is switched between a partially transparent non-superconducting state and a substantially non-transparent superconducting state by a modulation circuit. The resulting optical pulses transmitted through the superconducting layer are converted from the original wavelength to a lower wavelength by a frequency converting device.

Abstract: The invention features systems and methods for generating optical beams having substantially orthogonal polarizations for use in distance measuring interferometry. In one embodiment, the invention features a system including a source which during operation generates two nonparallel propagating source beams; and a retarder element positioned to receive the two nonparallel propagating source beams and convert them into two nonparallel propagating output beams that are polarized substantially orthogonal to one another. The system can further include a birefringent prism positioned to receive the two nonparallel propagating output beams and produce two parallel output beams.

Abstract: An angle modulator branches a light emitted from a light source 101 into a first light and a second light. An optical intensity modulator 104 subjects the first light to predetermined optical intensity modulation with a first electrical signal having a predetermined frequency fc outputted from a first signal source 1031. An optical angle modulator 105 subjects the second light to optical angle modulation with a second electrical signal outputted from a second signal source 1032. An photo-detector 107 homodyne-detects an optical-intensity-modulated signal and an optical-angle-modulated signal that have been coupled by an optical coupler 106 using its square-law detection characteristics, and produces an angle-modulated signal having a center frequency fc as a beat signal.

Abstract: In an optical communication system, efficient use of a Mach-Zehnder modulator requires accurate knowledge of the AC halfwave voltage at the desired modulation frequency. At high modulation frequencies this can be difficult to measure directly. A method of accurately measuring the AC halfwave voltage of a Mach-Zehnder modulator is described. The Mach-Zehnder modulator is biased at the peak of the transfer function curve and a sinusoidal signal of known amplitude and the desired frequency of measurement is applied. The optical power is measured with and without the sinusoidal signal. The ratio of the two optical powers is used in the Mach-Zehnder transfer equation to calculate the AC halfwave voltage.

Abstract: A demodulation system used in connection with an analog optical link that provides a wide dynamic range and SNR potential for large RF signal bandwidths. An optical carrier signal modulated with an RF signal is applied to an optical splitter in the demodulation system that splits the signal into first and second carrier signals. One of the carrier signals is applied to a coarse demodulator that provides either PM or FM demodulation to generate a demodulated signal representative of the signal that includes the RF signal and the additive inverse of an error signal. The output from the coarse demodulator is inverted, and integrated in the FM case, and then applied to a phase modulator along with the second optical carrier signal from the optical splitter.

Abstract: An optical component for modulation of polarization, a Mueller polarimeter and ellipsometer containing such an optical component. The optical component modulates a linearly polarized incident beam and returns a modulated beam. It includes a coupled phase modulator which modulates the incident beam twice in succession, the two modulations having the same frequency of &ohgr;/2&pgr;, and a coupling system modifying the polarization state of the light between the two modulations. The ellipsometer includes the means for detection of a measurement beam returned by a sample, which receives the modulated beam, in addition to a processing unit. The means of detection include a polarimeter producing n measured quantities representing the polarization states of the beam, and the processing unit produces m values for each of these quantities by Fourier transform, with n×m≧16 and m≧4, providing simultaneous access to the sixteen components of the Mueller matrix of the sample.

Abstract: A light modulation system, wherein a light source provides light of a certain wavelength to be modulated by a material layer, which forms part of a specifically configured plate assembly. The modulation layer is placed in the optical path of the light source. Further, the modulation layer is switched between first and second states, and cooperates with the light source to produce a train of pulses at a given pulse rate. The resulting optical pulses transmitted through the modulation layer are converted from the original certain wavelength to a lower wavelength by a frequency converting device.

Abstract: An input signal input to a 180 degree distributor is distributed as two signals, one of which with its phase inverted 180 degrees is input to a first modulation light source and the other with its phase unchanged is input to a second modulation light source; both signals are modulated with the intensity and the frequency of the light emission dependent on signal amplitude. The modulated signals are coupled by an optical coupler and subjected to heterodyne detection through a photodetector, where their light intensity modulation components offset each other when added and the multiplication of their light frequency components results in the frequency transition quantity doubling.

Abstract: A branch portion 107 branches a modulating signal into two signals in opposite phases. One of them is inputted to an FM laser element 102. The other one is adjusted in propagation delay and in amplitude and then is inputted to an IM suppressing laser element 110. The FM laser element 102 outputs an optical-frequency-modulated signal around a wavelength .lambda.1, whose optical intensity is also modulated. A local light source 104 outputs light at a wavelength .lambda.0, which is different from the oscillation wavelength .lambda.1 of the FM laser element 102 by .DELTA..lambda.. The IM suppressing laser element 110 outputs an optical-intensity-modulated signal. The three lights are combined and inputted to a photodetection portion 106.

Abstract: A time domain communications system wherein a broadband of time-spaced signals, essentially monocycle-like signals, are derived from applying stepped-in-amplitude signals to a broadband antenna, in this case, a reverse bicone antenna. When received, the thus transmitted signals are multiplied by a D.C. replica of each transmitted signal, and thereafter, they are, successively, short time and long time integrated to achieve detection.

Abstract: An electrical signal to be frequency-modulated is branched into first and second signals. An FM laser 102 oscillates light having a wavelength .lambda.1 in a steady state condition, and outputs an optical signal obtained by converting an amplitude change in the inputted first signal into an optical intensity change and an optical frequency change. An optical detecting portion 106, to which the optical signal from the FM laser 102 and light having a wavelength .lambda.0 outputted from a local light source 104 are inputted, converts an optical intensity modulation component of the inputted optical signal as a current amplitude change by operating square-law detection characteristics, and generates a beat signal at a frequency corresponding to a difference in wavelength .DELTA..lambda. between the two inputted optical signals. A discrimination portion 110 discriminates using a threshold value generated on the basis of the second signal and converts the beat signal into the pulse signal.

Abstract: A method and apparatus for modulating light, wherein a light source provides light of a certain wavelength to be modulated. A light modulating device is placed in the optical path of the light source. The resulting optical pulses transmitted through the light modulating device are converted from the original wavelength to a lower wavelength by a frequency converting device.

Abstract: Device for the detection and processing of optical radiations, comprising at least one quantum well having asymmetric composition, said well consisting of a stack of layers of materials having differing gaps.

Abstract: Mixing and modulating methods are described for nonlinear optical amplifiers (30) which can generate intermodulation products of radio-frequency signals in an optical carrier signal (26) without the penalty of an optical conversion loss and without the need for radio-frequency mixers, electro-optic modulators and expensive polarization-maintaining optical fibers. The radio-frequency signals can be applied to either a bias port (36) or an optical input port (32) of the optical amplifier and are used to upconvert and downconvert signals in phased-array antenna and remote antenna embodiments of the invention.

Abstract: An optical device, and an apparatus for detecting displacement information of an object using the optical device, include an electrooptical device for shifting a frequency of an incident beam by applying a voltage thereto and an optical system for converging the beam at least in a plane including an application direction of the voltage and traveling direction of the beam, and for decreasing a degree of change of the diameter of the converged beam at least in the plane so as to reduce the diameter of the beam incident on the electrooptical device at least in the application direction.

Abstract: An optical frequency shifter is provided to change the frequency of a coherent input light beam by imparting periodic increases in phase to the beam. This increase in phase is caused by ferroelectric liquid crystals (FLCs) in conjunction with quarter wave plates. The FLCs are repeatedly switched on and off by electrical signal generators, adding phase shift in steps, which in turn results in a higher output optical frequency.

Abstract: A frequency shifter for modulating the frequency of an incident light beam is disclosed. This frequency shifter includes an electro-optic crystal portion to be arranged at an incident position, an electrode arranged on the electro-optic crystal portion, a voltage application unit for applying a voltage to the electro-optic crystal portion via the electrode, and a unit which is arranged at least at a portion of the electro-optic crystal portion to uniformize the temperature of the electro-optic crystal portion.

Abstract: In an optical communication system for transmitting an optical fiber which may include an optical amplifier comprising an optical isolator, a polarization control system comprises at a send end a launch polarization controller for giving a launched state to the signal beam launched to the optical fiber. Received at a receive end as a received beam of a received state of polarization, the signal beam is split by polarization into first and second beams, each including a reception component of the modulating frequency and of a variable optical intensity. A detection signal is produced from the first and the second beams to have the modulating frequency and a variable electric intensity. Controlled by a launch controller supplied with the detection signal, the launch polarization controller keeps the launched state to minimize at the receive end the electric intensity.

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: A power beam tube is biased to supply a constant current to an EO crystal used as part of a frequency modulation circuit for FM laser radar. Integration of the constant current by the EO crystal's capacitance generates the desired ramp voltage waveform. A correction current is easily added to the circuit. The circuit effectively removes the EO crystal driver circuitry from the control loop, increasing the speed of the frequency modulator loop about ten times.

Abstract: An optical modulator includes two cladding layers of different conductive types, a light absorption layer formed between the cladding layers for propagating incident light and for absorbing the light in response to a voltage applied between the cladding layers, and an optical waveguide layer formed between the cladding layers and optically connected to the light absorption layer, for propagating the light.

Abstract: An optical system in which optical circulators with polarization plates are used for light modulation of plane polarized light waves. The light modulation is used for black and white printing, grey scale printing and for adjustment of beam intensity of plane polarized light waves.

Abstract: The present invention relates to a high performance nonlinear optical device by utilizing an optical medium of large second order nonlinear optical effects, which has acceptable processability and stability. The second-order nonlinear optical device of the present invention comprises an optical element of a monoclinic crystal of 4-hydroxy-3-methoxy-4'-nitrostilbene represented by the formula (I): ##STR1## said crystal belonging to space group P2.sub.1, point group #4, said optical element having at least one substantially optically smooth surface.

Abstract: An optical FM modulation system includes a continuous wave optical light source for producing an optical carrier wave; integration means, responsive to an FM modulating signal, for generating a phase signal representative of the phase variations corresponding to the frequency variations of the FM modulating signal; and an electro-optic phase modulator, responsive to the electrical signal representative of the phase variations, for shifting the phase of the optical carrier wave to modulate the frequency of the optical carrier wave as a function of the modulating signal.

Abstract: A coupled quantum well electro-optical modulator, whose semiconductor structure is composed of one or of a plurality of successions formed by two layers capable of forming quantum wells, of a barrier layer which separates the two layers and of an intrinsic layer which separates the succession from other possible successions, where in presence of an electric field the absorption threshold of the light radiation shifts towards shorter wavelengths.

Abstract: An optically-coupled high frequency amplifier is disclosed herein. The ampliifer of the present invention includes a laser and a receiver coupled by an optical beam. The amplifier further includes a modulator responsive to an input signal for modulating the optical beam generated by the laser. The receiver produces an output signal in response to the modulated optical beam. A specific embodiment of the present invention further includes impedance matching means for increasing the maximum operating frequency of the laser and the receiver.

Abstract: An infra red radiation modulator comprises a p type silicon substrate 1 having spaced n type and p type doped regions 2, 3 having respective doping concentrations of approximately 10.sup.20 and 10.sup.16 /cm.sup.3. A signal source 11 provides a bias voltage between the doped regions 2,3 via electrodes 4 for modifying the concentration of free carriers in the substrate between the doped regions and therefore the response of the modulator to incident infra red radiation. By appropriate control of the bias voltage the modulator can be caused to modulate, chop, filter or spectrally scan the incident radiation.