Showing papers on "Signal beam published in 2003"

Polytopic multiplex holography

Abstract: Disclosed is a multiplexing method and apparatus that allows holograms to be spatially multiplexed with partial spatial overlap between neighboring stacks of holograms. Each individual stack can additionally take full advantage of an alternate multiplexing scheme such as angle, wavelength, phase code, peristrophic, or fractal multiplexing, for example. An amount equal to the beam waist of the signal beam writing a hologram separates individual stacks of holograms. Upon reconstruction, a hologram and its neighbors will all be readout simultaneously. An filter is placed at the beam waist of the reconstructed data such that the neighbors that are read out are not transmitted to the camera plane. Alternatively, these unwanted reconstructions can be filtered out with an angular filter at an intermediate plane in the optical system that has a limited angular passband.

Collinear holography

Abstract: Collinear holographic memory is proposed and demonstrated. "Reference beam" and "signal beam" are bundled on the same axis, and irradiated on the recording medium through a single objective lens. This method enables us to reconstruct the hologram image with a collinear optical configuration.

Optically tunable superprism effect in nonlinear photonic crystals

Abstract: An analysis of the tunable superprism effect in a two-dimensional nonlinear photonic crystal is presented. We show that, by shifting the photonic bands of the crystal through the Kerr effect induced by a pump beam, one can tune the refraction angle of a transmitted signal beam over tens of degrees. We also demonstrate that the optical power required to tune the refracted angle is dramatically reduced if the frequency of the pump beam is close to a bandgap edge.

Optical storage system based on scanning interferometric near-field confocal microscopy

Abstract: A near-field, interferometric optical microscopy system includes: a beam splitter positioned to separate an input beam into a measurement beam and a reference beam; a mask positioned to receive the measurement beam, the mask comprising at least one aperture having a dimension smaller than the wavelength of the input beam, wherein the mask aperture is configured to couple at least a portion of the measurement beam to a sample to define a near-field probe beam, the sample interacting with the near-field probe beam to define a near-field signal beam; a detector having an element responsive to optical energy; and optics positioned to direct at least a portion of the reference beam and at least a portion of the near-field signal beam to interfere at the detector element.

Apparatus and method for vacuum-based nanomechanical energy force and mass sensors

Abstract: A doubly clamped beam has an asymmetric piezoelectric layer within the beam with a gate proximate to the beam within a submicron distance with a gate and beam dipole. A suspended beam is formed using a Cl 2 /He plasma etch supplied at a flow rate ratio of 1:9 respectively into a plasma chamber. A parametric amplifier comprises a NEMS signal beam driven at resonance and a pair of pump beams driven at twice resonance to generate a modulated Lorentz force on the pump beams to perturb the spring constant of the signal beam. A bridge circuit provides two out-of-phase components of an excitation signal to a first and second NEMS beam in a first and second arm. A DC current is supplied to an AC driven NEMS device to tune the resonant frequency. An analyzer comprises a plurality of piezoresistive NEMS cantilevers with different resonant frequencies and a plurality of drive/sense elements, or an interacting plurality of beams to form an optical diffraction grating, or a plurality of strain-sensing NEMS cantilevers, each responsive to a different analyte, or a plurality of piezoresistive NEMS cantilevers with different IR absorbers.

Existence and stability of rigid photovoltaic solitons in an open-circuit amplifying or absorbing photovoltaic medium.

Abstract: A different type of photovoltaic soliton is predicted for open-circuit photovoltaic media with a gain provided by two-wave mixing. Such solitons are a result of a double balance, i.e., loss is balanced by gain and diffraction is balanced by nonlinearity that is due to both, photovoltaic effects and two-wave mixing. Exact bright and dark analytical solutions are obtained under the condition that the signal beam is much weaker than the pump beam. Such solitons have fixed amplitude and width for the fixed values of the system parameters and hence are named rigid photovoltaic solitons. When the pump beam is switched to a background illumination, rigid photovoltaic solitons can become previously observed photovoltaic solitons. Numerical simulations show that rigid photovoltaic solitons are stable against small perturbations.

Hologram recording/reproducing method and hologram recording/reproducing device

Abstract: A method for holographic recording and reproducing includes a recording process and a reproducing process. In the recording process, a coherent reference beam is spatially modulated in accordance with information to be recorded to generate a signal beam, and the signal beam is converged. The converged signal beam enters and passes through a recording medium made of a photosensitive material. A diffraction grating area according to a light interference pattern is created in a portion where a 0th-order beam and a diffraction beam of the signal beam interfere with each other inside the recording medium. In the reproducing process, a reproduced wave corresponding to the signal beam is generated by illuminating the diffraction grating area with the reference beam.

Existence and property of spatial solitons in a photorefractive dissipative system

Abstract: A dissipative photorefractive system is considered, which consists of a biased photorefractive crystal and a pump beam with a uniform spatial distribution. A signal beam couples coherently with the pump beam by codirectional degenerate two-beam coupling and hence obtains a gain. It is shown that the signal beam can evolve into a steady-state spatial bright (or dark) soliton that is a result of double balance, i.e., loss is balanced by gain, and diffraction is balanced by nonlinearity due to the spatially nonuniform screening of the applied field and to the process of two-beam coupling. Such solitons have fixed amplitude and width for fixed values of system parameters and hence are known as rigid screening (RS) solitons. RS solitons differ from previously observed screening solitons in their properties and physical origin and can exist whether the crystal possesses a focusing or a defocusing nonlinearity. If the pump beam is switched to a background illumination, RS-soliton solutions can reduce to screening-soliton solutions. Numerical simulations show that RS solitons are stable relative to small perturbations.

Nearly diffraction-limited signal generated by a lower beam-quality pump in an optical parametric oscillator

Abstract: The beam quality of an optical parametric oscillator (OPO) within a singly resonant, confocal-positive branch unstable resonator is investigated. Resonator configurations have been found in which the beam quality of the outgoing signal exceeds the beam quality of the pump. Cavity magnification and pump-pulse duration are found to determine the signal beam quality. It is shown that signal M2 decreases with increasing pump-pulse duration for a given cavity magnification. In an experimental demonstration of a LiNbO3 OPO within an unstable resonator, pumped by a multitransversal mode beam, a signal beam with an almost-single transversal mode has been generated, whereas the multitransversal mode behavior of the pump beam is projected on the idler beam.

Bit error rate in a free-space laser communication system with a partially coherent signal beam

Abstract: Average bit error rates in a free-space laser communication system can be reduced by the use of a partially (spatially) coherent transmitted signal beam. When the spatial coherence of the transmitted signal beam is reduced intensity fluctuations (scintillations) decrease, leading to a reduction in the bit error rate of the optical communication link. A model that offers a method for calculating optimal system performance with full consideration of the lognormal turbulent channel and source beam characteristics is described. The impact of atmospheric turbulence strength and degree of source coherence on the average bit error rate is examined.

Design and laboratory characterization of a highly efficient all-solid-state 200-mJ UV light source for ozone DIAL measurements

Abstract: Design and laboratory characterization of a highly efficient all solid state 200 mJ UV light source for ozone dial measurements We are carrying out initial laboratory tests of an all solid state UV source designed to generate 200 mJ pulses of 320 nm light based on sum-frequency mixing of the 532 nm second harmonic of an Nd:YAG pump laser with 803 nm light derived from a nanosecond optical parametric oscillator. The sum-frequency stage was designed to obtain mixing efficiency approaching 60% by carefully matching the spatial and temporal properties of the 532 nm and 803 nm pulses. The nearly equal balance of 532 nm to 803 nm photons required an injection-seeded Nd:YAG pump laser and an OPO exhibiting exceptional signal beam quality and unusually high conversion efficiency. The OPO was designed to meet these requirements by employing a high Fresnel-number image-rotating nonplanar ring cavity producing signal beams with M-squared of approximately 3 that was pulsed self-injection seeded with the goal of obtaining greater than 75% conversion of pump energy into the signal and idler. This design can easily be modified to produce other UV wavelengths in the range of 300 nm to 320 nm.

Holographic recording/reproducing apparatus and reproducing apparatus for holographically recorded information

Abstract: A holographic recording/reproducing apparatus includes a splitter unit for splitting a laser beam into a first laser beam for generating a signal beam and a second laser beam which serves as a reference beam, a spatial light modulator for spatially modulating the first laser beam in accordance with information to be recorded, the modulated first laser beam serving as the signal beam, and a first lens system for focusing the signal beam and the reference beam onto a holographic recording medium. In a recording process, the signal beam and the reference beam are guided through one and the other half-regions separated along the optical axis of the first lens system. In a reproduction process, only the reference beam is guided through one of the half-regions and a signal reproduction beam from the holographic recording medium is guided through a second lens system in the other half-region.

Holographic rom system

Abstract: A holographic ROM system includes a light source (200) for emitting a laser beam; an expanding unit (204) for expanding the laser beam; and a mask (206) for modulating a certain portion of the expanded laser beam to thereby generate a signal beam which is directly provided to a holographic medium (208) and sifting the remainder portion of the expanded laser beam to thereby generate a reference beam which is provided to a conical mirror (210) reflecting the reference beam toward the holographic medium. The holographic medium is composed of a recording region onto which both the reference beam and the signal beam are projected; and a transparent region which passes through the reference beam sifted by the mask, to thereby provide the reference beam to the conical mirror.

Method and device for non-destructive material inspection by laser ultrasonic wave

Abstract: PROBLEM TO BE SOLVED: To allow very precise, accurate and reliable inspection, of course when a material surface is a specular face, and even when a rough surface such as a surface of a concrete structure. SOLUTION: In this nondestructive material inspection device, a pulse laser beam from a pulse laser 20 is emitted toward the material surface of a measured object via a movable mirror 7 to generate an elastic wave (ultrasonic wave), a laser beam from a continuous oscillation laser 1 for a signal is branched by a polarization beam splitter 4, one thereof is emitted as a probe beam to the material surface coaxially with the pulse laser beam via the movable mirror 7, a reflected beam is transferred as a signal beam with a wave front deformed by an influence of a scattering face on the material surface and the elastic wave, and phase-modulated, the signal beam and a reference beam are made to get incident, crossed with a prescribed angle, into a laser beam interferometer by a photorefractive crystal 9, and the presence of a defect in an inside of a material is detected based on a change in the phase modulation of an interfered beam therein. COPYRIGHT: (C)2005,JPO&NCIPI

Mechanical optical switch

Abstract: The utility model discloses a single-end mechanical optical switch, comprising a multi-optical fiber collimator, a fixed reflector and an active reflector; wherein, the multi-optical fiber collimator comprises N (N is more than or equal to 1) ports for inputting signal beam and M (M is more than or equal to 2) ports for outputting signal beam; the fixed reflector is composed by a multilateral prism plated with a piece of reflective film; the active reflector is driven by a driving device with a relay The utility model can realize signal-ended N*M light path conversion as the input and the output are fixed in a multi-optical fiber collimator, and has the advantages of simple structure, few elements and low cost

Transparent Nonlinear Optical Polymers for All-Optical Wavelength Converters in Optical Fiber Communications

Abstract: After synthesizing two chromophores with imine, we prepared acrylic nonlinear optical (NLO) polymers that contained the chromophores for all-optical wavelength converters in optical fiber communication. The polymers show high d 33 , 35 pm . V -1 , at 1.55 μm (pumping beam), considering their low losses, -3.0 dB.cm -1 , at a wavelength of 0.785 μm (near second harmonic signal beam of the pumping beam). This result means that the polymers are good candidales for wavelength converters of an approximately 1.55 μm signal beam.

Vertical-cavity saturable-absorber intensity modulator

Abstract: We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture, that exploits the optical saturation of absorption in semiconductor quantum wells. The modulation section of the modulator, which is composed of quantum wells placed within a Fabry–Perot cavity, is optically controlled by an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer and grown in a single epitaxial step. The modulation section and the in-plane laser share the same medium; therefore, efficient coupling between the control beam and the signal beam is achieved. The device was successfully used for active mode locking of an erbium-doped fiber laser.

Saturable absorber intensity modulator

Abstract: We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture that exploits saturation of absorption in semiconductor quantum wells pumped optically. The modulation section, composed of quantum wells placed within a Fabry-Perot cavity, is exposed to an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer. Since the modulation section and the in-plane laser share the same medium, an efficient coupling between the control beam and the signal beam is achieved. Design guidelines and device performance are presented. We demonstrate that the modulator provides an efficient light modulation mechanism that is sufficient to actively mode-lock an erbium-doped fiber laser.

Method of determining properties of patterned thin film metal structures using transient thermal response

Abstract: The present invention measures a structure including multiple narrow metallic regions, each being disposed between neighboring regions comprising a second, non-metallic material. One step of the method is exciting the structure by irradiating it with a spatially periodic excitation field made up of excitation stripes in order to generate a thermal grating. 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; and determining at least one property of the structure based on a thermal component of the signal waveform.

Efficient all solid-state UV source for satellite-based lidar applications.

Abstract: A satellite-based UV-DIAL measurement system would allow continuous global monitoring of ozone concentration in the upper atmosphere. However such systems remain difficult to implement because aerosol-scattering return signals for satellite-based lidars are very weak. A suitable system must produce high-energy UV pulses at multiple wavelengths with very high efficiency. For example, a nanosecond system operating at 10 Hz must generate approximately 1 J per pulse at 308-320 nm. An efficient space-qualified wavelength-agile system based on a single UV source that can meet this requirement is probably not available using current laser technology. As an alternative, we're pursuing a multi-source approach employing all-solid-state modules that individually generate 300-320 nm light with pulse energies in the range of 50-200 mJ, with transform-limited bandwidths and good beam quality. Pulses from the individual sources can be incoherently summed to obtain the required single-pulse energy. These sources use sum-frequency mixing of the 532 nm second harmonic of an Nd:YAG pump laser with 731-803 nm light derived from a recently-developed, state-of-the-art, nanosecond optical parametric oscillator. Two source configurations are under development, one using extra-cavity sum-frequency mixing, and the other intra-cavity sum-frequency mixing. In either configuration, we hope to obtain sum-frequency mixing efficiency approaching 60% by carefully matching the spatial and temporal properties of the laser and OPO pulses. This ideal balance of green and near-IR photons requires an injection-seeded Nd:YAG pump-laser with very high beam quality, and an OPO exhibiting unusually high conversion efficiency and exceptional signal beam quality. The OPO employs a singly-resonant high-Fresnel-number image-rotating self-injection-seeded nonplanar-ring cavity that achieves pump depletion > 65% and produces signal beams with M 2 ≈ 3 at pulse energies exceeding 50 mJ. Pump beam requirements can be met in the laboratory using a commercial Nd:YAG laser system, but only after extensive modifications.

Multi-watt diffraction-limited picosecond pulses from a diode-pumped Nd:YVO4 amplifier with a photorefractive phase conjugate mirror

Abstract: We demonstrate>4 W and 7.2 ps output of a double-pass Nd:YVO4 slab amplifier with a photorefractive ring phase conjugate mirror. A double-pass gain of 190 and optical extraction efficiency of >20% were obtained. The amplified signal beam exhibits a TEM00 profile with beam propagation parameters Mx2<1.4 and My2<1.1.

Ring-shaped prism of a holographic ROM system

Abstract: A holographic system for storing data on an interference pattern in a hologram storage medium includes a light source for emitting a laser beam, a beam splitter, modulating means and a refractive material. The beam splitter divides the laser beam into a reference beam and a signal beam and the modulating means modulates the signal beam to generate a modulated signal beam. The refractive material refracts the reference beam to generate a refracted reference beam, wherein the refracted reference beam interferes with the modulated signal beam in the hologram storage medium to generate the interference pattern.

Programmable 2D laser marking device based on a pulsed UV image coherent amplifier

Abstract: We present a novel technique for engraving microscopic 2D patterns in one step with a UV pulsed laser by means of a versatile programmable approach. The laser beam is divided to an expanded low energy signal beam which is spatially modulated by a LCD modulator and a higher energy pump beam with a plane homogeneous wave front. Both beams are superposed in a highly magnesium doped photorefractive lithium-niobate crystal where an energy transfer towards the weaker signal beam takes place. The spatially modulated and amplified signal beam is then de-magnified and imaged onto the surface where the image has to be engraved. The need for the coherent amplifier rises out of the fact that LCDs are unable to withstand the high energy throughput required for etching. The combination of the amplifier with the amplitude modulator leads to a faster and more flexible solution than laser marking with pixel-by-pixel raster-scan, or fixed mask projection mode. Such a technique can thus be applied to identify valuable items by imprinting a smart and personalized 2D code onto its surface.

Dynamic waveguides and gratings in photorefractive crystals

Abstract: This chapter is an overview of the photorefractive effect, the important photorefractive nonlinear processes and common photorefractive materials. In Section 2, the formation of steady-state spatial solitons by laser beam propagation through photorefractive crystals (PRC) with optical activity and absorption is theoretically and experimentally described. The spatial soliton features, which characterize the dynamic waveguide built in PRC, are analyzed. The soliton polarisation dynamics reaches a stable behavior under high external electric fields. Two-wave mixing and self-diffraction in dynamic harmonic and inharmonic gratings, induced by lasers in PRC, are presented in Section 3. The diffraction efficiency and beam amplification can reach high values, with promising potential in optical interconnections and storage. Dynamic and adaptive gratings by double phase conjugation (DPC) in PRC are discussed in Section 4. High phase conjugated reflectivity, high coupling transmission efficiency and robust interconnections of mutually incoherent lasers are achieved in DPC using Rh:BaTiO3 crystals.

Method and apparatus for storing and retrieving a sequence of digital paga data

Abstract: In a storing mode of an apparatus for storing and retrieving a sequence of digital page data, a first/second complex reference beam and a modulated signal beam converge on a storing location to generate a sequence of first/second interference patterns to be sequentially stored on a holographic medium. A shift selectivity of the first complex reference beam is larger than that of the second complex reference beam so that the second interference pattern is used as a servo pattern to sequentially determine where the first interference patterns have been stored.

All-optical 3R regenerator using solitary wave interactions

Abstract: A method and apparatus for all-optical signal regeneration in fiber optic communications networks is provided. The process utilizes solitary wave interactions in various nonlinear optical media to re-shape, re-amplify and re-time optical signals that have traveled over large distances of fiber-optic cable. The device consists of an optical clock generator synchronized to the system clock, recovered from the input signal by a clock recovery unit. The output of the optical clock is then used to produce a solitary wave in the nonlinear material that collides with the coincident signal beam. The net result is an all-optical signal regenerator. A multi-channel device capable of providing signal regeneration on multiple wavelengths using a single clock recovery and optical clock generator assembly is also disclosed.

Optimizing transverse photo-electromotive force detectors for laser ultrasonic applications

Abstract: The sensitivity of the adaptive photoelectromotive-force (photo-EMF) detectors arranged in the conventional transverse configuration and optimized for laser ultrasonic applications is analyzed It is shown that for the devices based on bipolar photoconductors operating under typical conditions, ie with approximately {\rm 10 \times 10} pixels in the detected speckle-like signal wave, the amplifier input noise current {\rm \approx 1 \hspace{0167em} pA/\sqrt {Hz},} and the probe beam wavelength of \mgreek{l} \approx 08 \hspace{0167em} \mgreek{m} m; the optimal matching with the preamplifier can be achieved with a detected signal beam power P S greater than ≈01 mW The limit on the sensitivity of these optimized photo-EMF detectors (with the inter-electrode spacing equal to 5 optimal fringe periods) found to be determined by the noise of the detector itself and is approximately a factor of 14 below the fundamental limit set by the shot noise of the detected signal power In particular, for P_{S} \approx

Optical transceiver, and method of manufacturing the same

Abstract: The invention provides an optical transceiver capable of simplifying the manufacturing process. An optical transceiver includes a transparent substrate having a surface emitting laser mounted thereon, a transparent substrate with a photo detector mounted thereon, a transparent substrate formed with diffraction gratings, and a transparent substrate formed with a diffraction grating adhered with each other in layers. The signal beam emitted from the surface emitting laser is introduced to the diffraction grating by the diffraction grating, converged by the diffraction grating, and introduced into the optical fiber connected to the sleeve. The signal beam emitted from the optical fiber connected to the sleeve is introduced toward the diffraction grating by the diffraction grating, converged by the diffraction grating, and introduced into the photo detector.

Preparation of grating device by utilizing ultrashort laser pulse and method for implementing holographic storage

Abstract: The invention provides a method of preparing diffraction-grating devices by using ultra-short laser pulse and that of realizing the holographic memory. The former method is as follows: use the spectra system to separate the ultra-fast laser pulse into two or more beams which arrive on the surface of in the body of double-photon absorbing polymer materials and overlap in time and space to obtain the interference stripes; by modualting the parameters of the beam number, the included angles and phases between eacho ther, intensity and so on, prepare one-dimensional, two-dimensional or three-dimensional minute-cycle diffraction-grating structure. The latter method is as follows: one separated beam in the former method is coupled with the information signal by space-light modulator and the information signal beam interferes with the reference beam,