Showing papers on "Signal beam published in 2007"

Technical limitations to homodyne detection at audio frequencies.

Abstract: Homodyne detection relies on the beat between a relatively strong local oscillator (LO) field at the carrier frequency and a signal beam with sidebands centered around the carrier frequency. This type of signal detection, or signal readout, is widely used in quantum optics applications and is expected to be used in advanced interferometric gravitational wave detectors. We investigate experimentally the limitations to making such measurements in a laboratory environment at audio frequencies. We find that beam jitter noise, electronic noise of the photodetectors, and the LO intensity noise can limit the homodyne detection in this frequency band, and we discuss potential solutions.

Adaptive interferometry of protein on a BioCD

Abstract: Adaptive spinning-disk interferometry is capable of measuring surface profiles of a thin biolayer with subnanometer longitudinal resolution. High-speed phase modulation in the signal beam arises from the moving surface height profile on the spinning disk and is detected as a homodyne signal via dynamic two-wave mixing. A photorefractive quantum-well device performs as an adaptive mixer that compensates disk wobble and vibration while it phase-locks the signal and reference waves in the phase quadrature condition (2 relative phase between the signal and local oscillator). We performed biosensing of immobilized monolayers of antibodies on the disk in both transmission and reflection detection modes. Single- and dual-analyte adaptive spinning-disk immunoassays were demonstrated with good specificity and without observable cross-reactivity. Reflection-mode detection enhances the biosensing sensitivity to one-twentieth of a protein monolayer, creates a topographic map of the protein layer, and can differentiate monolayers of different species by their effective optical thicknesses. © 2007 Optical Society of America OCIS codes: 170.3890, 160.5320, 120.3180.

Optical amplification in Ho3+-doped transparent oxyfluoride glass ceramics at 750nm

Abstract: Positive transient optical gain has been demonstrated in Ho3+-doped transparent oxyfluoride glass-ceramics. A pump and probe experiment has been designed to show this result. High power laser pulses at 532nm were used as the pump source to strongly populate the Ho3+S25:F45 level due to nonresonant ground state absorption. Low power cw laser radiation at 750nm was used as the probe beam. The signal beam stimulates the emission associated with the Ho3+S25:F45→I75 electronic transition at 750nm. In addition to this, the high power pump pulses provide population inversion between the S25:F45 and I75, initial and final states of the transition, respectively, giving rise to the optical amplification of the signal beam. A gain coefficient of 3.7cm−1 (∼16dB∕cm) was obtained for a pump energy density of about 135mJ∕cm2 and a signal beam power density of 6μW∕cm2.

Compact, single chip-based, entangled polarization-state photon sources and methods for generating photons in entangled polarization states

Abstract: Various embodiments of the present invention are directed to compact systems for generating polarization-entangled photons. In one embodiment of the present invention, a polarization entangled-photon state source comprises a single transmission layer (912, 1112, 1312, 1500, 1600) configured for transmitting electromagnetic radiation. The transmission layer includes a beamsplitter (902, 1102, 1302) and a down-conversion device (904, 1104), both of which are configured to convert a pump beam into first and second signal beams and first and second idler beams. The transmission layer also includes a mode converter (906, 1106, 1306) configured to invert electric and magnetic field components of both the first signal beam and the first idler beam, and a combiner (908, 1108, 1308) configured to receive the first and second beams and the first and second idler beams and output the first and second signal beams and the first and second idler beams in an entangled polarization states.

Optical transmission apparatus

Abstract: In an optical transmission apparatus, optical power of each of wavelength contained in a wavelength multiplexing signal is measured, a measured value of the optical power of each wavelength is compared with a predetermined threshold value, a total value of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a total value of signal beam power, and a total value of the measured values of the optical power, which are less then the threshold value, is calculated as a total value of ASE power. The number of the measured values of the optical power, which are equal to or larger than the threshold value, is calculated as a wavelength count of the signal beams contained in the wavelength multiplexing signal. A signal-to-ASE ratio is calculated from the total value of the signal beam power and the total value of the ASE power. The optical power of the wavelength multiplexing signal inputted to an optical amplifier is measured, and a target value of the automatic level control (ALC) is determined by use of the measured values of the wavelength count, the signal-to-ASE ratio and the optical power of the wavelength multiplexing signal in order to execute the ALC of the optical amplifier so that the optical power of each of the wavelengths in the wavelength multiplexing signal outputted from the optical amplifier, becomes constant.

All-optical switching and nonlinear optical properties of HBT in ethanol solution

Abstract: This paper demonstrates an all-optical switching model system comprising a single pulsed pump beam at 355 nm and a CW He–Ne signal beam at 632.8 nm with 2-(2'-hydroxyphenyl)benzothiazole (HBT) in ethanol solution. The origins of the optical switching effect were discussed. By the study of nonlinear optical properties for HBT in ethanol solvent, this paper verified that the excited-state intramolecular proton transfer (ESIPT) effect of HBT and the thermal effect of solvent worked on quite different time scales and together induced the change of the refractive index of HBT solution, leading to the signal beam deflection. The results indicated that the HBT molecule could be an excellent candidate for high-speed and high-sensitive optical switching devices.

Direct detection of optical phase conjugation in a colloidal medium

Abstract: Degenerate four-wave mixing is demonstrated using an artificial Kerr medium and is evidenced by directly observing the phase conjugation of a vortex signal beam. The nonlinear susceptibility is produced by a refractive index grating created in a suspension of dielectric microscopic particles optically confined in the intensity grating distribution of two interfering laser beams.

Optical tomography method & device

Abstract: A method for optical tomography is adapted to measure a medium, and includes the following steps: (A) generating a two-frequency mutually correlated low-coherence beam, an optical path difference of the beam being smaller than a coherence length; (B) focusing the beam on different depth positions of the medium such that the beam becomes a signal beam after being reflected by the medium; and (C) analyzing the signal beam reflected by the medium using a signal processing unit that includes a lens and a pinhole located at a focal point of the lens so as to obtain a sectioning image of the medium.

Observation of two-dimensional holographic photovoltaic bright solitons in a photorefractive-photovoltaic crystal

Abstract: Two-dimensional holographic photovoltaic bright spatial solitons are observed in a Cu:K0.25Na0.75Sr1.5Ba0.5Nb5O15 crystal in which two coherent laser beams, a signal beam, as well as a strong and uniform pump beam at 532nm are coupled to each other via two-wave mixing. Such solitons originate from the self-trapping of the signal beam due to both photovoltaic effects and holographic focusing effects.

Method of conducting an all-optical NAND logic operation controlled from a long distance

Abstract: Logic gates are the fundamental building blocks in any digital data-processing circuit. We propose a new method to implement a NAND logic operation controlled from a long distance. To realize it we consider two types of Gaussian pulses: the control beam and the signal beam. The signal beam propagates first through an electro-optic modulator and then through a nonlinear waveguide, whereas the control beam propagates directly through the optical fiber. Controlling the applied voltage of the electro-optic modulator, we can change the phase relation between the pulses. Hence a NAND switching operation can be realized at a very long distance in the optical fiber.

Optical transmission device

Abstract: An optical transmission device capable of preventing deterioration in the transmission quality of a signal beam A wavelength-multiplexed signal beam from a transmission path is split by a splitter, and the split signal beams are input to first and second optical paths, respectively An add/drop unit for adding/dropping a wavelength-multiplexed signal beam is removably insertable in the second optical path A switch outputs the wavelength-multiplexed signal beam, received from one of the first and second optical paths, to an optical amplifier The optical amplifier amplifies the wavelength-multiplexed signal beam output from the switch and outputs the amplified signal beam to a subsequent circuit A supervisory controller collects alarm information from the optical transmission device as well as from other optical transmission devices, and controls the switch in accordance with the collected alarm information such that the wavelength-multiplexed signal beam from the second optical path is input to the optical amplifier

Multiple-channel mid-infrared optical parametric oscillator in periodically poled MgO: LiNbO3

Abstract: We report a compact all-solid-state mid-infrared optical parametric oscillator with wide tunability using periodically poled 5 mol % MgO-doped LiNbO3 with a multiple-channel structure design and pumped by a compact diode-pump solid-state laser operating at 1.064 μm. Wide tunability from 1.44 to 1.58 μm at the signal beam wavelength and from 3.28 to 4.11 μm at the idler beam wavelength was achieved by both varying the temperature and translating the crystal through the resonator and the pump beam with no realignment required. The tuning performance and its related factors were analyzed, and at the same time the output performance as well as the effect of mid-infrared absorption of idler beam was investigated.

Optical noise reduction for dc-removed coaxial holographic data storage.

Abstract: A method of reconstructing positive and negative images from Fourier holograms recorded without the dc components is demonstrated by use of a coaxial holographic storage system. Reconstructed images are obtained by adding a phase-modulated dc component of the signal beam on reading. Contrast reversal of the reconstructed images can be achieved by reversing the readout reference pattern. This method can realize not only optical noise reduction but also less consumption of the dynamic range of the recording medium, potentially contributing to increasing the number of multiplexed holograms.

Two-wavelength switching with 1.55 μm VCSOA

Abstract: Two-wavelength switching of a signal beam by a control signal at a different wavelength is demonstrated for the first time in a 1550 nm vertical cavity semiconductor optical amplifier (VCSOA). This result offers promise for the use of VCSOAs in all-optical switching/routing applications.

System for generating reference beam angle control signal and holographic information recording and/or reproducing apparatus employing the system

Abstract: A system for generating a reference beam angle control signal and a holographic information recording and/or reproducing apparatus including the system are provided. When record of a two-dimensionally (2D) modulated signal beam superposed in the same volume of a holographic medium is called a book, the system includes: a first photo-detector and a second photo-detector arranged to detect signal beams reproduced from first and second adjacent books disposed on both sides of a specific book that is to be reproduced from the holographic medium; and a signal processing unit arranged to obtain a reference beam angle control signal for controlling the incident angle of a reference beam emitted to the holographic medium using a differential signal between output signals of the first and second photo-detectors.

Quasistable bright dissipative holographic solitons in photorefractive two-wave mixing system

Abstract: The dynamical evolution of both signal and pump beams are traced by numerically solving the coupled-wave equation for a photorefractive two-wave mixing system. The direct simulations show that, when the intensity ratio of the pump beam to the signal beam is large enough, the pump beam presents a common decaying behaviour without modulational instability (MI), while the signal beam can evolve into a quasistable spatial soliton within a regime in which the pump beam is depleted slightly. The larger the ratio is, the longer the regime is. Such quasistable solitons can overcome the initial perturbations and numerical noises in the course of propagation, perform several cycles of slow oscillation in intensity and width, and persist over tens of diffraction lengths. From physical viewpoints, these solitons actually exist as completely rigorous physical objects. If the ratio is quite small, the pump beam is apt to show MI, during which the signal beam experiences strong expansion and shrinking in width and a drastic oscillation in intensity, or completely breaks up. The simulations using actual experimental parameters demonstrate that the observation of an effectively stable soliton is quite possible in the proposed system.

60-dB-dynamic-range short-pulse measurement from an 8-bit CMOS camera

Abstract: We have developed a simple detection scheme that uses an 8-bit CMOS camera and spans over 60-dB dynamic range. By use of noise reduction techniques, the 8-bit CMOS camera yields a 40-dB dynamic-range signal, which is further increased by 20 dB by making a replica of the signal beam on another part of the detector chip. We have experimentally validated this scheme in a scanning and a single-shot autocorrelator.

Optical retrodirective tracking system approach using an array of phase conjugators for communication and power transmission

Abstract: A new concept for a retrodirective tracking system applicable for communication and power transmission is proposed. In the proposed concept, the power transmitter utilizes a receiver's pilot signal to obtain information about its direction by conjugating the signal's phase inside a nonlinear medium. Power is therefore transmitted back to the receiver by the phase-conjugated signal beam. The power can be concentrated by an array of phase conjugators, which provides a large aperture so that the intensity can be increased on the receiver's photovoltaic panels compared to a single element. Controlling the phase and the direction of the readout beams in the four-wave-mixing process provides control over the interference pattern, its position, and its size. A numerical analysis is given for the phase and spot size control, and measurements with two Co-doped SrxBa1−xNb2O6 (Co:SBN) crystals confirm the occurrence of interference that is achieved for the case of two beams.

Tracking system by phase conjugation for laser energy transmission

Abstract: We propose a new concept for a retro-directive tracking system applicable for communication and power transmission. In the proposed concept, the power transmitter utilizes a beacon emitted from the receiver to obtain information about its direction by conjugating its phase inside a nonlinear medium. Power is therefore transmitted back to the receiver by the phase conjugated beam. The power can be amplified by an array of phase conjugators which provides a large aperture so that the intensity can be increased on the receiver's photovoltaic panels compared to a single element. A system design provides the basic understanding of this setup and basic experiments are conducted with two Co-doped Sr X Ba 1-X Nb 2 O 6 (Co:SBN) crystals. We confirm the occurrence of interference of two beams that are generated by four wave mixing from a divergent signal beam. In areas of constructive interference, we could observe a higher intensity than the single non-interfering beams provides.

Apparatus and method for holographic recording and reproducing

Abstract: A holographic recording and reproducing apparatus is provided. The holographic recording and reproducing apparatus includes a signal-beam spatial light modulating unit that displays a signal beam pattern for a signal beam, a reference-beam spatial light modulating unit that displays a reference beam pattern for a reference beam, and a controller that controls the mode of the signal beam pattern and that of the reference beam pattern. The controller controls the modes of at least two signal beam patterns and the modes of at least two reference beam patterns. A first reference beam is made to interfere with a first signal beam based on first recording data to record the data as a first hologram in a predetermined area of the holographic recording medium. A second reference beam is made to interfere with a second signal beam based on second recording data to record the data as a second hologram such that the second hologram is superimposed on the first hologram.

New Coaxial Interference Method for Consumer Holographic Memory

Abstract: We have developed a new coaxial interference method for the next-generation storage system. A signal beam and a reference beam are coaxially arranged and focused into a holographic medium using a bifocal lens. We can easily downsize the system because the optics is very simple. The reference beam is focused on the mirror surface of the medium, and the signal beam is defocused on this surface. A semicircular reference pattern is used to select normal playback or phase conjugate playback in a reproducing process. We have recorded a single hologram and a multiplexed hologram in a photopolymer medium with this method. These holograms are reconstructed successfully. We have found that our interference method has a 4 µm shift selectivity and excellent characteristics for the next-generation high-capacity optical memory.

Holographic recording/reproducing apparatus having aperture of variable size

Abstract: Provided is a holographic recording/reproducing apparatus including an aperture device having aperture of variable size. The holographic recording/reproducing apparatus includes a light source, an optical system to divide light emitted from the light source into a recording reference beam and a recording signal beam, and direct the recording reference beam and the recording signal beam to a same location of a holographic recording medium, a spatial light modulator (SLM) to modulate the recording signal beam into a two-dimensional signal pattern, a two-dimensional photodetector to detect a reproducing signal beam that is refracted via the holographic recording medium, and the aperture to limit a size of a spot of the reproducing signal beam, wherein the size of the aperture is variable.

Sensing system for a forest fire having millimeter-wave passive imaging system

Abstract: A Forest fire monitoring system which has a passive millimeter wavelength signal detector is provided to monitor the forest fire in real-time in bad weathers by receiving signals at a millimeter wavelength band according to a temperature of a forest. A millimeter wave antenna array(21) receives a millimeter signal due to a specific temperature of an object. An LNA(Low Noise Amplifier)(22) removes noises from the millimeter signal and amplifies the millimeter signal. A detector(24) detects a necessary image signal. A beam former(25) controls a width of a millimeter signal beam, which is received from the antenna array. A phase shifter(26) suppresses an interference between the signals, which are received at the antenna array and amplified in the LNA. A transmission line(23) couples the LNA, the phase shifter, and the detector with one another. A digital signal processor(27) controls the beam former and processes digital image signals. A wireless radio antenna(28) transmits millimeter image signals and site images to a control center.

Enhancing all-optical switching by localizing the control and signal light fields in the same defect region

Abstract: We suggest an efficient mechanism for all-optical switching in one-dimensional photonic heterostructures based on the combined use of two resonant modes that have strong enhancement of their electric fields in the same defect region. By exciting the low-quality resonant mode with the low-intensity pump beam, one can very efficiently shift the spectral position of the high-quality resonant mode and thus control the propagation of a signal beam. For a AlGaAs/SiO2 heterostructure with two GaAs defect layers, we numerically demonstrate all-optical switching at a peak pumping intensity lower than 20 mW/mm2. Moreover, it is of great benefit to practical application that the frequency interval between the two resonant modes is adjustable in a wide range.

Design of a short-focal-length double-Fourier-transform-lens system for holographic storage

Abstract: A short-focal-length double-Fourier-transform-lens system for holographic storage was designed. The system is minimized by propagating signal beam and reference beam along a common optical axis. In order to obtain a compact configuration and high information density, the front and the rear Fourier-transform lens have short focal length (33 and 30 mm, respectively). The multiconfiguration optimization method is adopted to correct aberrations of the object region and meet the requirement of reference beam. The designed system, whose total numerical aperture for signal beam and reference beam is 0.60, achieves diffraction-limited imaging quality.

Performance analysis of field-of-view shifted Shack-Hartmann wavefront sensor based on splitter

Abstract: We report on a field-of-view shifted Shack–Hartmann wavefront sensor based on a splitter designed to measure the wavefront information of object light with strong background. The analysis results indicate that increasing the ratio of the signal beam intensity to the incoming beam intensity and reducing the sampling frequency of CCD2 (detecting the pure background light) can properly enhance the SNR (signal-to-noise ratio) of the object light. A special noise removing algorithm was presented to enhance the centroid measuring accuracy, and it was proved to be effective against the residual noises caused by the differences between the two beam paths. The experimental results indicate that the field-of-view shifted Shack–Hartmann wavefront sensor based on a splitter can exactly measure the wavefront information from the object with strong background.

Holographic information recording/reproducing apparatus and method for seeking books in the same

Abstract: Provided are a holographic information recording/reproducing apparatus in which positions of books can be accurately ascertained in a holographic recording medium, and a method for seeking books in the same. The apparatus includes an aperture plate disposed in an optical path of a signal beam reproduced from a reference beam that is incident on a holographic recording medium, and having an opening for restricting a width of the signal beam; one or more photodetectors installed on a surface of the aperture plate along a circumference of the opening; and a book position calculator to calculate positions of one or more books from the output of the photodetectors, wherein a cross-section of the reference beam incident on the holographic recording medium is larger than the size of the one or more books.

Perpendicular all-optical control of interactional optical spatical soliton pair

Abstract: In photoisomerization polymer, the perpendicular optical control of the optical spatial soliton interaction is simulated by numerical method. Under control, the properties of two interacting solitons are damaged, the signal beam can give birth to phenomena such as the two beams to join together, or to detach and so on. We also give a physical explanation of the phenomena, that they are determined by the difference in the initiatial phases of the beams, the incident position of control-beam and so on. The effect of perpendicular optical control of interaction solitons can be applied to optical interlinkage, optical waveguide and so on.