Showing papers on "Signal beam published in 2001"

Performing selected optical measurements with optical coherence domain reflectometry

Abstract: A system and method for performing selected optical measurements on a sample is provided utilizing an optical coherence domain reflectometer which includes a diffraction grating. A broad band light source produces light having a short coherence length. A beamsplitter splits the light into a signal beam and a reference beam. A reference mirror is disposed to receive the reference beam. A lens brings the signal beam to focus on the sample. A diffraction grating receives reflections from the sample and from the reference mirror, the reflections being incident on the diffraction grating with respect to said diffraction grating normal such that a positive diffraction order from one of the reflections and a negative diffraction order from the other one of the reflections and a negative diffraction order from the other one of the reflections propagate along a common path. A lens collects the diffracted order from the diffraction grating directed along the common path and brings the diffracted orders to focus on a detector, the detector producing an output of said positive and negative diffracted orders received. A computer processes the output from the detector. In other versions of the invention, reflections from the sample are not directed onto the diffraction grating but instead are combined with a diffracted order from reflections from the reference mirror.

Laser-induced incandescence for soot particle size and volume fraction measurements using on-line extinction calibration

Abstract: A novel technique for two-dimensional measurements of soot volume fraction and particle size has been developed. It is based on a combined measurement of extinction and laser-induced incandescence using Nd:YAG laser wavelengths of 532 nm and 1064 nm. A low-energy laser pulse at 532 nm was used for extinction measurements and was followed by a more intense pulse at 1064 nm, delayed by 15 ns, for LII measurements. The 532-nm beam was split into a signal beam passing the flame and a reference beam, both of which were directed to a dye cell. The resulting fluorescence signals, from which the extinction was deduced, together with the LII signal, were registered on a single CCD detector. Thus the two-dimensional LII image could be converted to a soot volume fraction map through a calibration procedure during the same laser shot. The soot particle sizes were evaluated from the ratio of the temporal LII signals at two gate time positions. The uncertainty in the particle sizing arose mainly from the low signal for small particles at long gate times and the uncertainty in the flame temperature. The technique was applied to a well-characterized premixed flat flame, the soot properties of which had been previously thoroughly investigated.

Ultrashort-pulse laser machining system employing a parametric amplifier

Abstract: A method and apparatus are provided for increasing the energy of chirped laser pulses to an output in the range 0.001 to over 10 millijoules at a repetition rate 0.010 to 100 kHz by using a two stage optical parametric amplifier utilizing a bulk nonlinear crystal wherein the pump and signal beam size can be independently adjusted in each stage.

Optical amplification in nematics doped with carbon nanotubes

Abstract: We present results on the orientational photorefractive effect in a mesogenic nematic doped with multiwalled carbon nanotubes. Efficient coherent-beam amplification of a signal beam by energy exchange with a pump beam was observed in homogeneous cells of the doped liquid crystal E7 at electric fields of ∼0.5 V/μm. Photorefractive gains as high as 103 cm−1 are achieved in the Raman–Nath regime. It is found that the gain coefficient depends strongly on the externally applied dc voltage, the pump/probe intensity ratio and the total input intensity.

Holographic optical information recording/reproducing device

Abstract: An optical information recording/reproducing device reproduces digital data recorded in a form of interference fringes produced by two coherent beams in a hologram disk, by projecting a coherent beam to the hologram disk and receiving a reproduction signal beam obtained by diffraction by means of a two-dimensional photodetector array. The holographic optical information recording/reproducing device includes a tunable coherent light source that emits the coherent beam, and a control section controls and optimizes a wavelength of the tunable coherent light source according to position information of the reproduction signal beam on the two-dimensional photodetector array. Thus, a holographic optical information recording/reproducing device is provided that is capable of maintaining a sufficient reproduction signal intensity and reproducing signals stably while undergoing a minimum of cross-talk, even in the case where the optimal reproduction wavelength varies due to a variance of media, a change of a temperature of a recording medium, etc.

Method and device using x-rays to measure thickness and composition of thin films

Abstract: An apparatus for measuring a property (e.g., thickness or composition) of at least one film in a sample (e.g., a multilayer film stack contained in a microelectronic device) is disclosed. The method executed in the apparatus features the steps of generating a coherent x-ray pulse, delivering the coherent x-ray pulse to a region on the sample to generate a signal beam, detecting the signal beam to generate an electrical signal, and analyzing the electrical signal to determine the property (e.g., thickness) of the film.

Unstable resonator optical parametric oscillator based on quasi-phase-matched RbTiOAsO 4

Abstract: We demonstrate improved signal and idler-beam quality of a 3-mm-aperture quasi-phase-matched RbTiOAsO4 optical parametric oscillator through use of a confocal unstable resonator as compared with a plane-parallel resonator. Both oscillators were singly resonant, and the periodically poled RbTiOAsO4 crystal generated a signal at 1.56 µm and an idler at 3.33 µm when pumped at 1.064 µm. We compared the beam quality produced by the 1.2-magnification confocal unstable resonator with the beam quality produced by the plane-parallel resonator by measuring the signal and the idler beam M2 value. We also investigated the effect of pump-beam intensity distribution by comparing the result of a Gaussian and a top-hat intensity profile pump beam. We generated a signal beam of M2 ≈ 7 and an idler beam of M2 ≈ 2.5 through use of an unstable resonator and a Gaussian intensity profile pump beam. This corresponds to an increase of a factor of approximately 2 in beam quality for the signal and a factor of 3 for the idler, compared with the beam quality of the plane-parallel resonator optical parametric oscillator.

Dark and bright photovoltaic spatial solitons in photorefractive crystals with positive refractive-index perturbation

Abstract: We have demonstrated, for what is believed to be the first time, that in a photorefractive crystal with positive refractive-index perturbation a two-dimensional dark or bright photovoltaic spatial soliton can be formed in the same crystal by a signal beam and a background beam of different wavelengths. We discuss the conditions on the effective Glass constants and the absorption coefficients of the background and signal beams in determining the formation of the spatial soliton.

Laser communication system with source tracking

Abstract: A free space laser communication system that maintains dynamic alignment is presented. The system comprises two laser transceivers positioned a distance apart. Each transceiver includes the following components. A beacon laser is provided for transmitting a beacon beam at a first wavelength in a beam having a first divergence. A signal laser is provided for transmitting a signal beam carrying information to be transmitted to the other transceiver. A special telescope system is provided for collecting both the incoming beacon beam and the incoming signal beam from the other transceiver and for transmitting at least an outgoing signal beam. In a preferred embodiment the special telescope images the pupil of the telescope onto a tracking mirror. The tracking mirror pivots at least tilt and tip. The beacon beam is reflected from the tracking mirror and focused on a CCD array which monitors the direction of the beacon beam and provides a feedback signal to the tracking mirror to maintain the tracking mirror in positions which direct the beacon beam to a predetermined position on the CCD array and also directs the signal beam through a small aperture to a signal detector.

Analysis of the generation of amplitude-squeezed light with Gaussian-beam degenerate optical parametric amplifiers

Abstract: We investigate the generation of amplitude-squeezed states with degenerate optical parametric amplifiers that are pumped by focused Gaussian beams. We present a model that facilitates the calculation of the squeezing level for an experimentally realistic configuration in which there is a Gaussian input signal beam that has the same confocal parameter and waist location as the Gaussian pump beam, with no restriction on the interaction length-to-confocal parameter ratio. We show that the 3-dB squeezing limit that was thought to be imposed by the Gaussian pump profile can be exceeded in the (previously uninvestigated) tight-focusing regime. We find the maximum possible amplitude squeezing in this regime to be 4.65 dB. However, it is possible to increase the squeezing level further by spatially filtering the tails of the output signal beam, resulting in squeezing levels in excess of 10 dB.

System and method for performing selected optical measurements utilizing an optical coherence domain reflectometer

Abstract: A system and method for performing selected optical measurements on a sample is provided utilizing an optical coherence domain reflectometer which includes a diffraction grating. A broad band light source produces light having a short coherence length. A beamsplitter splits the light into a signal beam and a reference beam. A reference mirror is disposed to receive the reference beam. A lens brings the signal beam to focus on the sample. A diffraction grating receives reflections from the sample and from the reference mirror, the reflections being incident on the diffraction grating with respect to said diffraction grating normal such that a positive diffraction order from one of the reflections and a negative diffraction order from the other one of the reflections and a negative diffraction order from the other one of the reflections propagate along a common path. A lens collects the diffracted order from the diffraction grating directed along the common path and brings the diffracted orders to focus on a detector, the detector producing an output of said positive and negative diffracted orders received. A computer processes the output from the detector. In other versions of the invention, reflections from the sample are not directed onto the diffraction grating but instead are combined with a diffracted order from reflections from the reference mirror.

Cylindrical medium for storing holographic data and methods and apparatus for manipulating data using the cylindrical medium

Abstract: Holographic data is stored in a cylindrical crystal by directing a signal beam with data encoded therewith axially through an end face of the crystal, which signal beam interferes with a reference beam directed radially through the cylindrical side surface of the crystal. By rotating the crystal about its axis, numerous holograms are recorded therein an annular layer and by indexing the crystal axially the annular layers are stacked to further increase the storage capacity of the crystal. The holograms are read from the crystal by focusing a reference beam therethrough in a radial director for diffraction with the stored holograms to produce a defracted reference beam which emerges axially from the crystal. The diffracted reference beam is then read with a detector in the form of a CCD camera.

Confocal holographic optical storage with non-overlapping records

Abstract: The present invention relates to a method and a system for the storage of data in the form of volume holograms which do not mutually overlap. The storage medium consists of a high-sensitive material in the form of a plate of thickness D, in which a single hologram is essentially shaped as a cylinder with the minimal possible cross-section. The signal light beam is modulated with data and directed onto the plate-shaped storage material by means of a lens or a conventional optical system, illuminating an area of the material which, for a given amount of data, is the smallest possible. To record a hologram, a reference light beam is used, incident upon the storage material either from the same direction as the signal beam, or opposite thereto. The hologram is only written in the portion where the signal and the reference beams overlap.

Optical record medium, hologram record reproducing method, hologram record reproducing device, optical recorder and optical reproducing device

Abstract: PROBLEM TO BE SOLVED: To provide a hologram record reproducing method or the like which makes it possible to record a hologram by which an ample diffraction efficiency is achieved and read out without breakage the hologram recorded through the guided wave of a readout beam which causes an incidence upon the recording layer from the end face. SOLUTION: The light is subjected to the guided wave on the surface of a transparent substrate 11 at an incident angle greater than that of a determined value relative to this surface. A refractive index or an absorptive index is varied by the simultaneous irradiation of the signal beam and the reference beam each having a specified wavelength. The refractive index or the absorptive index varied is retained then an optical record medium 10 is used by which a recording layer 12 capable of recording the hologram is formed. When recorded, the hologram is recorded by simultaneously irradiating to the recording layer 12 the signal beam and the reference beam each having a prescribed wavelength. When reproduced, the recording layer 12 is subjected to the guided wave of a readout beam 3 of the wavelength which does not vary the refractive index or the absorptive index which is held by the recording layer 12. The hologram is reproduced by the diffracted light generated when the guided wave is forced to occur. This causes no problem with the guided wave loss upon being recorded. The recorded hologram can be reproduced without breakage upon being reproduced.

Observation of damage in PPLN

Abstract: Periodically-poled lithium niobate (PPLN) has been used to convert the 1.064 micrometer emission from a diode-pumped Nd:YAG laser to give an emission close to 4 micrometer. An acousto-optical Q-switch was used for generating short- duration, high-intensity pulses. Modulated waveforms are possible via direct modulation of the diode sources. A simple OPO configuration has been used with a resonated signal beam passing through a PPLN crystal in an oven. The pump beam has good beam quality, having an M2 of about 1.8 in each axis, and modulated average power in excess of 6 W. Damage has been observed to the output face of PPLN crystals over a range of pumping conditions and OPO configurations. The estimated damage threshold has been surprisingly low, of the order of 1.5 J/cm2. First observations indicated the damage occurring consistently at the output face of the crystal, but further analysis has indicated the presence of bulk damage, typically starting at domain boundaries.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Enhancement of two-wave coupling in a Ce:KNSBN crystal with optimum polarization of the writing beams

Abstract: We have improved the two-wave coupling amplification and the signal-to-noise ratio of an amplified signal with photorefractive cerium-doped potassium sodium strontium barium niobate (Ce:KNSBN) by employing optimum polarization orientation of the pump beam while the signal beam retains extraordinary polarization. The optimum polarization angle of the pump beam was found experimentally to be 30 degrees with respect to the extraordinary polarization direction in a symmetrically incident system. Nearly 1.9-times enhancement of the gain and nearly 3-times enhancement of the signal-to-noise ratio were achieved at a signal-to-pump beam intensity ratio of 1:40. At a beam intensity ratio of 1:2000, a two-wave coupling gain of nearly 500 was obtained, which is much higher than the gain previously reported. Modified coupled-wave equations that involve beam fanning with certain assumptions concerning the fanning parameters were used. The numerical solution is in good agreement with the experimental data. The results are compared with those obtained with a 45 degrees -cut BaTiO(3) crystal.

A self-doubling optical parametric oscillator based on aperiodically-poled lithium niobate

Abstract: Summary form only given. In this experiment, we construct a self-doubling optical parametric oscillator (SDOPO). It is based on a LiNbO/sub 3/ crystal that has a one-dimensional aperiodic grating structure. This grating structure is designed to quasi-phase-match both optical parametric oscillation (OPO) and second harmonic generation (SHG) processes simultaneously for a propagation direction along the x-axis of the crystal. When a beam at a wavelength of 790 nm pumps the SDOPO, a signal beam at a wavelength of 1140 nm and an idler beam at a wavelength of 2573 nm are generated along with the SHG of the signal beam at a wavelength of 570 nm. Waves corresponding to both interactions are polarized parallel to the c-axis of the crystal in order to utilize the highest nonlinear coefficient, d/sub 33/.

One-dimensional dark solitons in photovoltaic media with a positive perturbation refractive index

Abstract: We present a theory of photovoltaic(PV) spatial solitons(SS's), that includes the PV contribution of a background beam(BB). The theory predicts that a dark or a bright SS can be formed in the same crystal with positive refractive index perturbation (Δn). If the ratio (R) of the effective Glass constants(EGC) of the BB to that of the signal beam(SB) is 1. We have formed a one-dimensional dark PV SS in a crystal, as predicted.

Polychromatic photovoltaic spatial soliton

Abstract: A photovoltaic spatial soliton theory of duotone signal beam with monochrone background beam is presented, and a solution of bright soliton has been obtained by a numberical method. We have observed bright photovoltaic spatial solitons of polychromatic signal beam with monochrome background beam in a Cu:KNSBN crystal.

Remote sensing of optical absorption coefficient of object, e.g. patient's body part, uses separated beams of entangled pair photons

Abstract: Quantum theory states that light beams consist of pairs of photons, signal photons and idler photons; each of a pair being affected by the same event. The present application depends on the assumption that if the idlers were separated from the signal photons, they would still mirror the effects experienced by the signal photons. The output of a laser (1) is split into signal and idler beams. The signal beam (m) scans the patient (S), while the idler beam (e) is fed to a detector (I).

Double signal phase conjugation with a Cat conjugator

Abstract: The phase conjugate reflection of double signals, induced by the self-pumped phase conjugation, is demonstrated in a 16° cut Cu-doped potassium sodium strontium barium niobate (KNSBN) photorefractive crystal. The phase conjugate reflectivities of signals were measured versus the pump-signal beam ratio. A comparison was made between the signal's reflectivity with and without the presence of the other signal beam. The multi-region four-wave mixing model within the same crystal has been employed to explain the geometry performance and the experimental results.

Containerless photoacoustic spectroscopy using photorefractive interferometry

Abstract: Photoacoustic spectroscopy of gases is one of the most sensitive spectroscopic techniques available, often achieving part per million (ppm) or part per billion (ppb) sensitivity. This technique is usually performed by containing the gas sample within a cell coupled to an acoustic transducer. Imaging of photoacoustic response over an area requires scanning of the excitation beam. At the INEEL, research is underway to extend photorefractive dynamic holography to full field spectroscopic imaging without scanning. The photorefractive effect in Bismuth Silicon Oxide is exploited to demodulate the optical phase shift of a signal beam traversing the test gas and coincident with a tunable chopped excitation beam. Molecular absorption at the excitation wavelength produces heat that causes local expansion and subsequent acoustic wave radiation. A model of the photoacoustic absorption and optical phase detection process has been developed. Measurement and modeling results are presented that illustrate the ability of the method to detect water vapor and Hydrogen Fluoride concentrations in nitrogen atmosphere backgrounds near 800 nm, currently producing sensitivities in the 20-1000 ppm. Limitations of the technique and methods for extending to ppb sensitivities with infrared excitation are discussed.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Transmissivity measuring device

Abstract: PROBLEM TO BE SOLVED: To provide a transmissivity measuring device capable of measuring highly precisely a transmissivity of glass parts by using an excimer laser as a light source. SOLUTION: This measuring device has a beam splitting means for splitting a laser beam from the excimer laser into a signal beam and a reference beam, an inserting/removing means installed so as to be able to insert/remove a measuring object into/from an optical path of the signal beam, a polarizing means F1 for eliminating only P-polarized component or S-polarized component from the reference beam and a measuring means F2 for measuring the quantity of the beam eliminated by the polarizing means F1, and a polarizing means R1 for eliminating only the same polarized component as the polarized component eliminated by the reference beam from a transmitted beam when the measuring object is arranged in the optical path and the signal beam when the measuring object is taken out from the optical path and a measuring means R2 for measuring the quantity of the beam eliminated by the polarizing means R1. The transmissivity of the measuring object is measured by using signals obtained from the measuring means F2 and the measuring means R2.

Method and apparatus for recording information to optical recording medium

Abstract: PROBLEM TO BE SOLVED: To enable stable recording by sinking a recording medium into a liquid of a refractive index equal to or nearly equal to a refractive index of a transparent substrate, and recording information to a recording layer. SOLUTION: A hologram memory 1 is set to a holding device 22 in a container 21, and a liquid 24 having a refractive index nearly equal to a refractive index of transparent substrates 3 and 4 is injected to the container 21. The hologram memory 1 is made to completely soak in the liquid 24 and moreover soak in the liquid 24 up to each projection opening of a signal beam irradiation device 23A and a reference beam irradiation device 23B. A signal beam 10 and a reference beam 11 are emitted to the hologram memory 1 from the signal beam irradiation device 23A and reference beam irradiation device 23B. Each of the irradiating beams 10 and 11 advances in the liquid 24, hits the transparent substrate 3 of the hologram memory 1, passes into the transparent substrate 3 without being reflected at the interface between the liquid 24 and the transparent substrate 3, and intersects at a predetermined point in a recording layer 2, whereby information is recorded as a hologram.

Optical pickup and optical information recording/ reproducing device

Abstract: PROBLEM TO BE SOLVED: To provide an optical pickup which enables efficiently outputting light using the proximity field optical effect of the light and further efficiently detecting the light SOLUTION: This optical pickup is provided with a planar probe array 1 which collects a laser beam L from a light source on an optical recording medium and detects a signal beam from the optical recording medium and the planar probe array 1 has one micro-opening 5 or more having a diameter of <= wavelength of the beam and one photodetector 6 or more for detecting the signal beam from the optical recording medium on the same substrate 2 This optical pickup is further provided with an optical element 7 which collects an incident laser beam from the light source on the micro-opening 5, an optical element 8 which collects the signal beam from the optical recording medium on the photodetector 6 and an optical element 9 for separating the incident laser beam and the signal beam and, therefore, can detect the signal beam efficiently and stably without almost being influenced by the deviation of optical axis, etc

Active phased array antenna system for mobile satellite communication and beam control method for satellite tracking

Abstract: PURPOSE: An active phased array antenna system for a mobile satellite communication and a beam control method for satellite tracking are provided to track a satellite at a high speed, achieve a high gain and employ a wider electronic tracking range. CONSTITUTION: A receiving channel signal beam forming unit passes a plurality of channels through a phase shifter and combines signals. A tracking signal beam forming unit makes plural channel receiving signals into four groups and passes the same through the phase shifter to combine the signals. A tracking signal detecting unit detects size of the signal formed by the tracking signal beam forming unit. A phase tracking processing unit calculates a phase pointing error relative to the beams of the tracking signals based on signal strength detected by the tacking signal detecting unit and calculates a phase pointing error with respect to the receiving channel signal beams and the transmission signal beams. A tracking beam control unit calculates a phase variation value from the satellite pointing error of the tracking signal beams and controls a phase value of the phase shifter inside the receiving active phased array antenna. A receiving channel beam control unit calculates a phase variation value from the satellite pointing error of the receiving channel signal beams and controls the phase value of the phase shifter inside the receiving channel signal beam forming unit. A transmitting beam control unit calculates a phase variation from the satellite pointing error of the transmission signal beams and controls the phase value of the phase shifter inside the transmitting active phased array antenna.

Optical fiber type optical amplifier fabricated by collective connection packaging method

Abstract: PURPOSE: An optical fiber type optical amplifier fabricated by a collective connection packaging method is provided which collectively connects various fusing connection points in an arrangement capable of ribbon connecting to reduce the number of fusing connection points, thereby simplifying fabrication processes and decreasing packaging size. CONSTITUTION: An optical amplifier includes a front tap optical coupler(12) connected to an input port(11), a front optical isolator(13), and a WDM optical coupler(14) for combining an excited beam and a signal beam with each other to send the combined beam to an optical amplification fiber(15) serving as an amplification medium. The optical amplifier further has a back optical isolator(16) for preventing reverse flowing of an optical signal together with the front optical isolator, a gain smoothing filter(17) for smoothing a gate, a back tap coupler(18) for monitoring a light source, and an output port(19). Connection points among the above constituent elements are arranged in a ribbon form to be collectively connected, to minimize the number of fusing connection points(20).

Process and apparatus for generating at least three light bundles of different wavelength

Abstract: In a process and an apparatus for generating at least three light bundles (64, 66, 90) of different wavelength for displaying color images, one of these light bundles (66) having a longest wavelength and another of the light bundles (64) having a shortest wavelength, which light bundles are obtained by an OPO (56) and further nonlinear optical component elements from a signal beam and/or idler beam (58, 60) of the OPO (56) and/or a primary light bundle (50), from which a beam (52) exciting the OPO (56) is also derived, it is provided that at least a partial light bundle (52) is separated from the primary light bundle (50) for exciting the OPO (56), in that the light bundle (64) with the longest wavelength and the light bundle (66) with the shortest wavelength are obtained from the signal beam and/or idler beam (58, 60) of the OPO (56) by way of frequency multiplication and/or frequency mixing with another partial light bundle of the primary light bundle (50) by excluding components of light bundles other than the generated light bundles (90) with the shortest and longest wavelengths for image display.

High speed polarization mode dispersion compensator

Abstract: The present invention is directed to a continuously adjustable optical delay device (20) for delaying an optical signal beam (ab) and includes a variable delay element (32), a first electro-optic deflector (26) and a second electro-optic deflector (38), a first scan lens (28) and a second scan lens (36), and a deflector driver (46) for varying first and second electrical control signals to direct a first polarization optical signal beam (a) through different portions of the variable delay element (32). The variable delay element (32) is at least one prism (34). The present invention is also directed to a polarization mode compensator for correcting the effects of polarization mode dispersion.