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Showing papers on "Signal beam published in 2004"


Patent
26 Oct 2004
TL;DR: In this paper, the authors proposed a mixed-beam embodiment of the user-specific signal and the common signal in a mixed beam embodiment, where the processing circuitry ensures the users' signals are time-aligned and have a controlled phase difference when received at mobile stations in the sector cell.
Abstract: An antenna array in a radio node includes multiple antenna elements for transmitting a wider beam covering a majority of a sector cell that includes a common signal and a narrower beam covering only a part of the sector cell that includes a mobile user-specific signal. Transmitting circuitry is coupled to the antenna array, and processing circuitry is coupled to the transmitting circuitry. The processing circuitry ensures the user-specific signal and the common signal in a mixed beam embodiment are in-phase and time-aligned at the antenna array. In a steered beam embodiment, the processing circuitry ensures the user-specific signal and the common signal are time-aligned and have a controlled phase difference when received at mobile stations in the sector cell. In both embodiments, distortions in the common signal and the user-specific signal associated with their conversion from baseband frequency to radio frequency are also compensated. And in the steered beam embodiment, beam forming weights are used not only to radiate a narrower beam to the desired mobile user but also to direct a wider common signal beam to reach all mobile users in the cell.

114 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrated a mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave, which offers high modulation contrast for signals in the visible and near infrared spectral ranges.
Abstract: We have demonstrated a mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave. An optical fluence of 15mJ∕cm2 in the control channel is sufficient to achieve nearly a ten-fold intensity modulation of the signal beam reflected from a Glass ∕MgF2∕Ga structure. The mechanism depends on a nanoscale light-induced structural transformation in the gallium layer and has transient switching times of the order of a few tens of nanoseconds. It offers high modulation contrast for signals in the visible and near infrared spectral ranges.

80 citations


Patent
27 Sep 2004
TL;DR: In this paper, the authors proposed an optical coupling device including: at least a first input port for delivering an optical input signal beam that includes a plurality of wavelength channels; at least an output port for receiving an optical output signal beam; a wavelength dispersion element for spatially separating the plurality of wavelengths in the optical input signals to form a spatially separated wavelength channel beams; and a coupling device for independently modifying the phase of each of the spatially-separated wavelength channels such that, for at least one wavelength channel beam, a selected fraction of the light is coupled to
Abstract: An optical coupling device including: at least a first input port for delivering an optical input signal beam that includes a plurality of wavelength channels; at least a first optical output port for receiving an optical output signal beam; a wavelength dispersion element for spatially separating the plurality of wavelength channels in the optical input signal beam to form a plurality of spatially separated wavelength channel beams; an optical coupling device for independently modifying the phase of each of the spatially separated wavelength channel beams such that, for at least one wavelength channel beam, a selected fraction of the light is coupled to the first output port and a fraction of the light is coupled away from the first output port.

75 citations


Journal ArticleDOI
TL;DR: A BBO-based chirped-pulse optical parametric amplifier employing an angularly dispersed signal beam to yield a full-octave gain bandwidth, sufficient for the direct amplification of sub-10-fs pulses and the suppression of parasitic second harmonic generation of the signal beam.
Abstract: We propose a BBO-based chirped-pulse optical parametric amplifier employing an angularly dispersed signal beam to yield a full-octave gain bandwidth, sufficient for the direct amplification of sub-10-fs pulses. Numerical simulations show that this power-scalable amplifier configuration has a small-signal gain of 10(7) at a pumping intensity of 45 GW/cm(2). The additional phase-matching flexibility compared to alternative configurations permits the suppression of parasitic second harmonic generation of the signal beam.

66 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrated a new mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave, which offers high modulation contrast for signals in the visible and near infrared spectral ranges.
Abstract: We have demonstrated a new mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave. An optical fluence of 15 mJ/cm^2 in the control channel is sufficient to achieve nearly a 10-fold intensity modulation of the signal beam reflected from a Glass/MgF_2/Ga structure. The mechanism depends on a nanoscale light-induced structural transformation in the gallium layer and has transient switching times of the order of a few tens of nanoseconds. It offers high modulation contrast for signals in the visible and near infrared spectral ranges.

62 citations


Journal ArticleDOI
TL;DR: In this article, a self-organized light-wave network (SOLNET) is proposed for three-dimensional (3-D) optical wiring with optical Z-connections, where the self-organization is generated in a photorefractive material by self focusing of the two write beams from the two devices.
Abstract: This paper presents core technologies for a self-organized microoptical system (SELMOS) within optoelectronic computers; mass-productive fabrication processes of waveguide films and new types of self-organized lightwave networks (SOLNETs) for three-dimensional (3-D) optical wiring with optical Z-connections. Waveguide films are fabricated by the built-in mask method, which is reusable and can construct surface-normal mirrors/filters at one time within photolithographic accuracy. Beveled core edge walls are made by the tilted ultraviolet (UV) exposure through the built-in mask using a photodefinable material. Near- and far-field patterns reveal that the walls act as micromirrors for optical Z-connections. SOLNET is a network consisting of self-organized coupling waveguides between misaligned optical devices. The self-organization is generated in a photorefractive material by self-focusing of the two write beams from the two devices. Direct SOLNET, where wavelengths of the write beam and the signal beam are the same, is demonstrated using a laser diode. Reflective SOLNET, where one of the two write beams is replaced with a reflected write beam from the edge of the coupled device, realizes two-beam-writing SOLNET in a one-beam-writing configuration. It is especially effective when the coupled device cannot transmit write beams. The proof-of-concept is demonstrated both theoretically and experimentally. These results indicate a possibility to form 3-D optical wiring simply in SELMOS.

51 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated photon statistics in the signal beam generated by frequency nondegenerate parametric downconversion both with and without a seed field along the idler direction.
Abstract: We investigate photon statistics in the signal beam generated by frequency nondegenerate parametric downconversion both with and without a seed field along the idler direction. The experiments are performed on the signal generated in β-barium borate by a traveling-wave pump pulse that is the frequency-tripled output of an amplified Nd:YLF picosecond laser. The high powers obtained allow us to measure the number of photons with a simple detection technique. When both signal and idler fields are initially in their vacuum states, the generated fields are mixtures of equally occupied modes with thermal photon-number statistics.

48 citations


Patent
Takuya Tsukagoshi1
15 Mar 2004
TL;DR: In this paper, the authors proposed a holographic recording medium for phase information of light by projecting a signal beam and a reference beam thereonto, a reflective surface disposed on the opposite side of the recording layer as viewed in the direction of signal and reference beam incidence on the holographic medium and formed with a convex pattern or a concave pattern having a trapezoidal cross-section, a minimum width of convex surface of the convex patterns or concave surfaces of the concave patterns being set equal to or larger than a beam spot diameter of the signal beam or
Abstract: A holographic recording medium includes a recording layer in which data are to be recorded as phase information of light by projecting a signal beam and a reference beam thereonto, a reflective surface disposed on the opposite side of the recording layer as viewed in the direction of signal beam and reference beam incidence on the holographic recording medium and formed with a convex pattern or a concave pattern having a trapezoidal cross-section, a minimum width of a convex surface of the convex pattern or a concave surface of the concave pattern being set equal to or larger than a beam spot diameter of the signal beam or the reference beam at a diffraction limit thereof. According to the thus constituted holographic recording medium, it is possible to easily remove noise light contained in a signal beam and a reference beam.

36 citations


Patent
Takuya Tsukagoshi1
19 Apr 2004
TL;DR: In this paper, the authors propose a holographic recording and reproducing method for holographic data in which data are to be recorded as phase information of light by projecting a signal beam and a reference beam thereonto and a servo layer disposed on the opposite side of the recording layer as viewed in the direction of signal beam incidence on the HMD.
Abstract: A holographic recording and reproducing method for recording data in a holographic recording medium comprising a recording layer in which data are to be recorded as phase information of light by projecting a signal beam and a reference beam thereonto and a servo layer disposed on the opposite side of the recording layer as viewed in the direction of signal beam incidence on the holographic recording medium and having regions in which servo projections are formed by projecting the signal beam and the reference beam onto the holographic recording medium and reproducing holographic data from the holographic recording medium by projecting the reference beam onto the holographic recording medium, the holographic recording and reproducing method includes steps of setting an optical path of the signal beam so that the signal beam is projected onto other regions of the servo layer than the regions formed with the servo projections, setting an optical path of a servo beam different from that of the signal beam so that the servo beam is projected onto one of the regions of the servo layer in which the servo projections are formed after passing through an objective lens through which the signal beam passes and projecting the servo beam onto the servo layer along the thus set optical path of the servo beam.

35 citations


Patent
07 Jun 2004
TL;DR: An apparatus for recording or reading high areal density holographically stored information with high signal-to-noise ratio is described in this article, where a holographic imaging system consisting of a first numerical aperture and a first focal length and an additional optical system for filtering the signal beam is presented.
Abstract: An apparatus for recording or reading high areal density holographically stored information with high signal-to-noise ratio. The apparatus comprises a holographic imaging system for recording or reconstructing a holographic image, having a first numerical aperture and a first focal length and an additional optical system for filtering the signal beam, having a second numerical aperture and a second focal length, wherein the numerical aperture of the additional optical system is less than the numerical aperture of the holographic imaging system and/or the focal length of the additional optical system is greater than the optical length of the holographic imaging system.

35 citations


Journal ArticleDOI
TL;DR: In this article, a planar Doppler velocimetry (PDV) system was designed which was able to generate two beams from a single source separated in frequency by 690 MHz.
Abstract: A planar Doppler velocimetry (PDV) system has been designed which is able to generate two beams from a single source separated in frequency by 690 MHz. This allows a common-path imaging head to be constructed, using a single imaging camera instead of the usual camera pair. Both illumination beams can be derived from a single laser and a set of acousto-optic modulators used to affect the frequency shifts. One illumination frequency lies on an absorption line of gaseous iodine, and the other in a region of zero absorption. The beams sequentially illuminate a plane within a seeded flow and Doppler-shifted scattered light passes through an iodine vapor cell onto the camera. The reference beam that lies in a zero absorption region is unaffected by passage through the cell, and provides a reference image. The signal beam, the frequency of which coincides with an absorption line, encodes the velocity information as a variation in transmission dependent upon the Doppler shift. Images of the flow under both illumi...

Patent
25 Mar 2004
TL;DR: In this paper, a signal beam with data formed by superimposing pattern data, the pattern data representing a pattern in which a large number of plural kinds of pixels having different tone values are arranged in a two-dimensional manner, on an image data of respective pixels represented by tone values corresponding to density.
Abstract: A hologram recording method includes generating a signal beam with data formed by superimposing pattern data, the pattern data representing a pattern in which a large number of plural kinds of pixels having different tone values are arranged in a two-dimensional manner, on an image data of respective pixels represented by tone values corresponding to density, and recording a hologram by irradiating a converted beam formed by Fourier transformation of the generated signal beam with a lens and a reference beam to an optical recording medium.

Journal ArticleDOI
TL;DR: It is predicted that the photoisomerization nonlinearity can support steady-state dark and bright spatial solitons in the polymer and the dependence of the FWHM of the spatial soliton on wavelengths of the background beams and on the ratio of the intensity of thebackground beam to that of the signal beam.
Abstract: We present a theory for a new type of optical spatial soliton that is based on the angle hole burning mechanism of photoisomerization in some polymers. We predict that the photoisomerization nonlinearity can support steady-state dark and bright spatial solitons in the polymer. We also discuss the dependence of the FWHM of the spatial soliton on wavelengths of the background beams and on the ratio of the intensity of the background beam to that of the signal beam.

Patent
Takuya Tsukagoshi1
16 Jan 2004
TL;DR: In this article, the authors propose a holographic recording method for phase information of light by projecting a signal beam and a reference beam onto a recording medium, wherein an X direction is defined as the direction of a line of intersection between a plane including the optical axes of the signal and reference beam (incidence plane) and the recording plane of the recording medium.
Abstract: A holographic recording method for recording information as phase information of light by projecting a signal beam and a reference beam onto a recording medium, wherein an X direction is defined as the direction of a line of intersection between a plane including the optical axes of the signal beam and reference beam (incidence plane) and the recording plane of the recording medium, and the Y direction is defined as the direction of a line lying normal to the incidence plane and intersecting said line of intersection, comprises steps of using the reference beam modulated with a first phase code to record a first hologram at a predetermined position and using the reference beam modulated with a second phase code whose pattern is different from that of the first phase code to record at a position shifted in the Y direction a second hologram that partially overlaps the first hologram.

Patent
12 Nov 2004
TL;DR: In this paper, a waveguide type optical device utilizing a nonlinear refractive index change according to a large 3rd order nonlinear optical phenomenon is presented, where the pump beam is coupled to one arm of the signal beam waveguide.
Abstract: Disclosed is a waveguide type optical device utilizing a nonlinear refractive index change according to a large 3rd order nonlinear optical phenomenon. The waveguide type optical device includes a signal beam waveguide through which a signal beam propagates; and a pump beam waveguide through which a pump beam propagates, wherein the pump beam waveguide is disposed adjacent to the signal beam waveguide so that the pump beam can be coupled to the signal beam waveguide, the signal beam waveguide is made of nonlinear optical materials with large 3rd order nonlinear optical property and the pump beam waveguide is made of linear optical materials, and the wavelength range of the signal beam is different from that of the pump beam. By such a structure, the pump beam is coupled to one arm of the signal beam waveguide, thereby generating a 3rd nonlinear phenomenon on one arm of the waveguide through which the signal beam passes. Therefore, the waveguide optical device which implements an all-optical communication device operating as an optical device and can be integrated is provided.

Patent
20 Jan 2004
TL;DR: In this article, a femtolaser is used to read a data train in parallel and thus at almost real-time, using a sequence of interlinked Nonlinear Sampling-Gates.
Abstract: When sampled simultaneously by a set of synchronized high intensity beams, a device consisting of a sequence of interlinked Nonlinear Sampling-Gates, through which a signal beam propagates, generates a replica of the intensity of the signal beam, during the interaction period. The device may be implemented optically or electrically as an ultra-high speed parallel receiver and when sampled by a femtolaser may be used to read a data train in parallel and thus at almost in real time. The device may also be used to stretch, compress, multiplex, demultiplex, read headers and help switch data trains optically in communication networks.

Patent
13 Oct 2004
TL;DR: In this paper, the authors proposed an optical image measuring instrument equipped with a half mirror 6 for dividing the leaser beam from a low coherent light source into a signal beam S and a reference beam R; a frequency shifter 8 for shifting the frequency of the reference beam S; a reference mirror 9 and a piezoelectric element 9A both of which alter the light path length of the R; CCDs 21 and 22 for detecting the interference beam L, which is formed by superposing the S and the R on upon another by the half-mirror
Abstract: PROBLEM TO BE SOLVED: To provide an optical image measuring instrument capable of forming a three-dimensional image or the like, which is based of a tomographic image at every depth of matter to be measured, with high precision even if the matter to be measured is moved during measurement. SOLUTION: The optical image measuring instrument is equipped with a half mirror 6 for dividing the leaser beam from a low coherent light source into a signal beam S and a reference beam R; a frequency shifter 8 for shifting the frequency of the reference beam R; a reference mirror 9 and a piezoelectric elements 9A both of which alter the light path length of the reference beam R; CCDs 21 and 22 for detecting the interference beam L, which is formed by superposing the signal beam S and the reference beam R on upon another by the half mirror 6 to output a detection signal; an image forming part 51 for forming a tomographic images based on the detection signal; a measuring depth calculation means 53 for calculating the measuring depth of the tomographic images; and an image processing part 57 for arranging a plurality of the formed tomographic images in a measuring depth direction based on the measuring depth. In the image processing part 57, the three-dimensional image is formed on the basis of the arranged tomographic images. COPYRIGHT: (C)2006,JPO&NCIPI

Journal ArticleDOI
TL;DR: Angular dispersion of the signal beam inside the nonlinear media is introduced to improve the non-collinear phase-matching range as discussed by the authors, which can surpass one order of magnitude in some particular configurations.
Abstract: Angular dispersion of the signal beam inside the nonlinear media is introduced to improve the non-collinear phase-matching range. Simulations run for BBO crystals predict that bandwidth increase is possible for most of the application spectral range and that it can surpass one order of magnitude in some particular configurations.

Journal ArticleDOI
TL;DR: In this paper, the authors used adaptive CdTe:V photoelectromotive force (photo-EMF) detector for high-sensitivity broadband detection of laser-generated ultrasound.
Abstract: Results of experiments studying the utilization of adaptive CdTe:V photoelectromotive force (photo-EMF) detector for high-sensitivity broadband detection of laser-generated ultrasound are presented. Unlike widely used GaAs photo-EMF detectors, the devices used here demonstrate no significant electron-hole competition. This ensures effective detection of ≅1 nm surface displacements with ≅0.1 mW of the signal beam power in 10 MHz detection frequency band, even in simple transverse detector configuration. For the wavelength of λ=852 nm used in the experiments, the dielectric cutoff frequency of a typical device was approaching 1 MHz. This, in principle, enables monitoring of as-processed objects moving with in-plane velocities up to 10 m/s.

Journal ArticleDOI
TL;DR: Nonlinear laser wave mixing in a common graphite furnace atomizer is presented as a zeptomole-level, sub-Doppler, high-resolution atomic absorption spectrophotometric method to obtain both excellent spectral resolution and detection sensitivity.
Abstract: Nonlinear laser wave mixing in a common graphite furnace atomizer is presented as a zeptomole-level, sub-Doppler, high-resolution atomic absorption spectrophotometric method. A nonplanar three-dimensional wave-mixing optical setup is used to generate the signal beam in its own space. Signal collection is efficient and convenient using a template-based optical alignment. The graphite furnace atomizer offers advantages including fast and convenient introduction of solid, liquid, or gas analytes, clean atomization environment, and minimum background noise. Taking advantage of the unique features of the wave-mixing optical method and those of the graphite furnace atomizer, one can obtain both excellent spectral resolution and detection sensitivity. A preliminary concentration detection limit of 0.07 parts-per-quadrillion and a preliminary mass detection limit of 0.7 ag or 8 zmol are determined for rubidium using a compact laser diode as the excitation source.

Journal ArticleDOI
TL;DR: In this article, a comprehensive analysis of the optically tunable superprism effect in a two-dimensional nonlinear photonic crystal is presented, and it is shown that, under certain circumstances, if one modifies the band structure of the crystal through the Kerr effect induced by a pump beam, the refraction angle of the transmitted signal beam can be tuned over tens of degrees.
Abstract: A comprehensive analysis of an optically tunable superprism effect in a two-dimensional nonlinear photonic crystal is presented. We demonstrate that, under certain circumstances, if one modifies the band structure of the crystal through the Kerr effect induced by a pump beam, the refraction angle of the transmitted signal beam can be tuned over tens of degrees. Two complementary geometries are considered, namely, air holes in a dielectric background and dielectric rods surrounded by air, and in both cases the TE and TM polarizations are studied. We also show that, because of the slow light effect, in both cases the optical power required to tune the refracted angle is dramatically reduced if the frequency of the pump beam is close to a photonic bandgap edge.

Journal ArticleDOI
TL;DR: In this article, an optical resonator with a quadratic medium coupled to an intra-cavity saturable absorber is shown to be able to generate large amplitude asymmetric pulses in the transverse section of the signal beam.

Patent
23 Jan 2004
TL;DR: In this article, a coherent light beam consisting of linear polarized P and S wave components having mutually orthogonal polarizations and frequencies ωP and ωS, respectively, is used to measure absorption and reduced scattering coefficients of a multiple scattering medium.
Abstract: In a method for measuring absorption and reduced scattering coefficients of a multiple scattering medium, a coherent light beam is outputted. The coherent light beam includes linear polarized P and S wave components having mutually orthogonal polarizations and frequencies ωP and ωS, respectively. Then, the coherent light beam is split into a signal beam and a reference beam, which include the P wave and S wave components. The signal beam is subsequently projected into the medium. Optical interference signals of the reference beam and the signal beam penetrating the medium are respectively detected and converted into heterodyne interference electrical signals. Thereafter, the two heterodyne interference electrical signals are compared to obtain amplitude attenuation and phase delay of the signal beam penetrating the medium, from which the absorption and reduced scattering coefficients of the medium at a position where the signal beam penetrated the medium are inferred.

Patent
09 Apr 2004
TL;DR: In this paper, a double-layered mask for modulating a signal beam with data to generate the modulated signal beam has a first and a second opaque film and a transparent plate inserted there between.
Abstract: In a holographic recording apparatus having a hologram medium for storing an interference pattern between a reference beam and a modulated signal beam, a double-layered mask for modulating a signal beam with data to generate the modulated signal beam has a first and a second opaque film and a transparent plate inserted therebetween. The first and the second opaque film face each other and have a plurality of first and second recording tracks, respectively. The first and the second recording tracks are alternately arranged, wherein the data to modulate the signal beam therewith are alternately embedded along the first and the second recording tracks such that one of two neighboring recording tracks is one of the first recording tracks and the other is one of the second recording tracks.

Journal ArticleDOI
TL;DR: In this paper, an all-optical wavelength converter using a polymeric Mach-Zehnder interferometer (MZI) comprised of an excited state intramolecular proton transfer (ESIPT) dye, 2,2′-{oxybis[4-(methoxyphenyl)quinoline-6,2-diyl]}bis(5-methoxideyphenol) (MQ).
Abstract: We designed and demonstrated an all-optical wavelength converter using a polymeric Mach–Zehnder interferometer (MZI) comprised of an excited state intramolecular proton transfer (ESIPT) dye, 2,2′-{oxybis[4-(4-methoxyphenyl)quinoline-6,2-diyl]}bis(5-methoxyphenol) (MQ). This MZI wavelength converter is composed of the MQ dye-doped polymeric waveguide and a thick light blocking metal film. A feature of this device is that one arm of the MZI can be irradiated by 355 nm pulses (signal beam), while the other arm was not, thus allowing a differential phase shift in the submicrosecond time scale. Because of the refractive index change of the ESIPT dye in one arm of interferometer upon irradiation with the signal beam, phase modulation of the continuous-wave probe light propagating in the irradiated arm of the MZI takes place, leading to the intensity modulation at the output defined by the signal beam, resulting in an all-optical wavelength converter, that is, the conversion of the signal modulation to output si...

Journal ArticleDOI
TL;DR: In this paper, the two-photon sub-wavelength interference can exist in a general spontaneous parametric down-conversion (SPDC) for both type I and type II crystals.
Abstract: We theoretically discuss one-photon and two-photon double-slit interferences for spontaneous and stimulated parametric down-conversions. We show that the two-photon sub-wavelength interference can exist in a general spontaneous parametric down-conversion (SPDC) for both type I and type II crystals. We propose an alternative way to observe sub-wavelength interference by a joint-intensity measurement which occurs for only type I crystal in a higher gain of SPDC. When a signal beam injects into the crystal, it may create two interference patterns by two stimulated down-converted beams, showing no sub-wavelength interference effect.

Patent
20 May 2004
TL;DR: In this paper, a holographic memory system includes a light source for generating a reference beam having a wavelength; and a photodetecting device for selectively detecting a reconstructed signal beam corresponding to the reference beam.
Abstract: A holographic memory system includes a light source for generating a reference beam having a wavelength; and a photodetecting device for selectively detecting a reconstructed signal beam corresponding to the reference beam. The photodetecting device includes a band-pass filter for transmitting light of a wavelength band including the wavelength of the reconstructed signal beam while blocking light having a wavelength deviating from the wavelength band; and a photodetecting unit for detecting the light transmitted through the band-pass filter.

Patent
23 Jun 2004
TL;DR: In this article, the authors used a spatially periodic laser intensity pattern in order to generate surface acoustic waves, and then diffracting a probe laser beam off the thermal grating to form a signal beam, detecting the signal beam as a function of time to generate a signal waveform, determining surface acoustic wave phase velocity from the waveform; and determining at least one property of the trench structures based on the dependence of surface acoustic Wave phase velocity on the parameters of the structure.
Abstract: The present invention uses ISTS to measure trenches with near- or sub-micron width. The trenches can be etched in a thin film on in a silicon substrate. One step of the method is exciting the structure by irradiating it with a spatially periodic laser intensity pattern in order to generate surface acoustic waves. Other steps are diffracting a probe laser beam off the thermal grating to form a signal beam; detecting the signal beam as a function of time to generate a signal waveform; determining surface acoustic wave phase velocity from the waveform; and determining at least one property of the trench structures based on the dependence of surface acoustic wave phase velocity on the parameters of the structure.

Proceedings ArticleDOI
TL;DR: In this paper, a photorefractive crystal is used to mix the diffusively scattered laser light with a reference beam and the phase modulation is converted to an amplitude modulation so that the API signal can be detected.
Abstract: Acousto-photonic imaging (API) is a dual-wave sensing technique in which a diffusive photon wave in a turbid medium interacts with an imposed acoustic field that drives scatterers to coherent periodic motion. A phase-modulated photon field emanates from the interaction region and carries with it information about the local opto-mechanical properties of the insonated media. A technological barrier to API has been sensitivity - the flux of phase-modulated photons is very small and the incoherence of the resulting speckle pattern reduces the modulation of the scattered light leading to low sensitivity. We report preliminary results from a new detection scheme in which a photorefractive crystal is used to mix the diffusively scattered laser light with a reference beam. The crystal serves as a dynamic holographic medium where the signal beam interferes with the reference beam, creating a photorefractive grating from which beams diffract. In addition, the phase modulation is converted to an amplitude modulation so that the API signal can be detected. Measurements of the API signal are presented for gel phantoms with polystyrene beads used as scatterers, showing a qualitative agreement with a simple theoretical model developed.

Patent
26 Nov 2004
TL;DR: In this article, an optical holographic device for recording a data page in a holographic medium is described, which consists of means (100) for generating a signal beam, means (201) for modulating the phase of the signal beam so as to encode the data page and means (102, 107, 108) for interfering the modulated signal beam with a reference beam inside the hologram medium.
Abstract: The invention relates to an optical holographic device for recording a data page in a holographic medium (106). The device comprises means (100) for generating a signal beam, means (201) for modulating the phase of the signal beam so as to encode the data page and means (102, 107, 108) for interfering the modulated signal beam with a reference beam inside the holographic medium. The invention also relates to a corresponding holographic read-out device, to a method for reading out a phase-modulated data page and to a holographic medium comprising at least one phase-modulated data page.