Showing papers on "Signal beam published in 2012"

Focused cylindrical vector beam assisted microscopic pSPR biosensor with an ultra wide dynamic range.

Abstract: A novel phase-sensitive surface plasmon resonance (pSPR) biosensor based on differential phase measurement between two cylindrical vector beams, namely radially polarized and azmuthally polarized beams, is proposed and studied in an inverted microscope. Different from a fixed angle or a relatively small angular range for SPR excitation in the attenuated total reflection (ATR) configuration, the signal beam focused by a total internal reflection fluorescence microscopic objective contains the entire angular range from 0 to the maximum angle given by the numerical aperture, leading to a dynamic range of 0.41 RIU which is over seven times wider than the best result of the ATR pSPR sensor. Moreover, with the technique of differential phase measurement between radial and azimuthal polarizations employed in our configuration, high sensitivity of ±9.05×10−8 refractive index unit/1 deg can simultaneously be achieved in principle. The proposed technique maintains the unique advantages in terms of securing high imaging resolution and sensitivity with an ultra-wide dynamic range simultaneously.

Hamiltonian tools for the analysis of optical polarization control

Abstract: The study of the polarization dynamics of two counterpropagating beams in optical fibers has recently been the subject of a growing renewed interest, from both the theoretical and experimental points of view. This system exhibits a phenomenon of polarization attraction, which can be used to achieve a complete polarization of an initially unpolarized signal beam, almost without any loss of energy. Along the same way, an arbitrary polarization state of the signal beam can be controlled and converted into any other desired state of polarization, by adjusting the polarization state of the counterpropagating pump beam. These properties have been demonstrated in various different types of optical fibers, i.e., isotropic fibers, spun fibers, and telecommunication optical fibers. This article is aimed at providing a rather complete understanding of this phenomenon of polarization attraction on the basis of new mathematical techniques recently developed for the study of Hamiltonian singularities. In particular, we show the essential role that play the peculiar topological properties of singular tori in the process of polarization attraction. We provide here a pedagogical introduction to this geometric approach of Hamiltonian singularities and give a unified description of the polarization attraction phenomenon in various types of optical fiber systems.

High-order Raman sidebands generated from the near-infrared to ultraviolet region by four-wave Raman mixing of hydrogen using an ultrashort two-color pump beam.

Abstract: A two-color pump beam consisting of a fundamental beam of a Ti:sapphire laser (35 fs, 802 nm) and a signal beam generated by optical parametric amplification (55 fs, 1203 nm) was utilized to generate multiple Raman sidebands by vibrational four-wave Raman mixing. The second harmonic emission (401 nm) was further employed as a seed beam for enhancing efficiency. Numerous sidebands emitting at 602, 481, 344, 301, 267, 241, 219, 200, and 185 nm were observed by irradiating the beam onto a screen coated with sodium salicylate. The spectral band width of these emission lines was capable of generating 0.9-fs optical pulses by Fourier synthesis.

Theory of polarization attraction in parametric amplifiers based on telecommunication fibers

Abstract: We develop from first principles the coupled wave equations that describe polarization-sensitive parametric amplification based on four-wave mixing (FWM) in standard (randomly birefringent) optical fibers. We show that in the small-signal case these equations can be solved analytically, and permit us to predict the gain experienced by the signal beam as well as its state of polarization (SOP) at the fiber output. We find that, independently of its initial value, the output SOP of a signal within the parametric gain bandwidth is solely determined by the pump SOP. We call this effect of pulling the polarization of the signal towards a reference SOP the polarization attraction, and we call the parametric amplifier the FWM polarizer (which can equivalently be called the fiber-optic parametric amplifier polarizer). Our theory is valid beyond the zero polarization mode dispersion (PMD) limit, and it takes into account moderate deviations of the PMD from zero. In particular, our theory is capable of analytically predicting the rate of degradation of the efficiency of the parametric amplifier, which is caused by the detrimental PMD effect.

Gaussian- versus flat-top-pumping of a mid-IR ZGP RISTRA OPO

Abstract: The influence of the pump intensity profile on the performance of a mid-IR ZGP RISTRA OPO at 6.45 µm is studied for a flat-top pump profile and compared to a Gaussian pump distribution at the same pump peak fluence of 0.81 J/cm2. Due to a coherent beam transformation a flat-top pump beam with a plane wavefront and excellent beam quality of M2≈1.25 is generated. The output of up to 5 mJ pulse idler energy (0.5 W average idler power) is identical in both cases, showing that flat-top pumping allows a reduction of the OPO crystal volume by 55 % while still maintaining a good output beam quality of M2<2.7 for the idler and M2<2.5 for the signal. The experimental results are compared to the SNLO RISTRA model and the limitations of the model are discussed.

High efficiency optical modulation at a telecom wavelength using the quantum Zeno effect in a ladder transition in Rb atoms.

Abstract: We demonstrate a high-efficiency optical modulator at ~1323 nm using the quantum Zeno effect in a ladder transition in a Rb vapor cell. The lower leg of the transitions represents the control beam while the upper leg of the transitions represents the signal beam. The cross-modulation of the signal beam transmission is observed as the control beam is intensity modulated, and is explained in terms of the quantum Zeno effect. We observe a modulation depth of near 100% at frequencies up to 1MHz and demonstrate modulation at speeds up to 75 MHz, with a 3 dB bandwidth of about 5 MHz, limited by the homogeneous linewidth of the intermediate state. We also describe how much higher modulation speeds could be realized by using a buffer gas to broaden the transitions. We identify and explain the special conditions needed for optimizing the modulation efficiency. Numerical simulations of modulation at ~1GHz are presented. The maximum modulation speed is found to scale with the pressure-broadened linewidth of the intermediate state, so that much higher speeds should be attainable.

Switchable multi perspective detector, optics therefore and method of operating thereof

Abstract: A secondary charged particle detection device for detection of a signal beam is described. The device includes a detector arrangement having at least two detection elements with active detection areas, wherein the active detection areas are separated by a gap (G), a particle optics configured for separating the signal beam into a first portion of the signal beam and into at least one second portion of the signal beam, and configured for focusing the first portion of the signal beam and the at least one second portion of the signal beam. The particle optics includes an aperture plate and at least a first inner aperture openings in the aperture plate, and at least one second radially outer aperture opening in the aperture plate, wherein the aperture plate is configured to be biased to one potential surrounding the first inner aperture opening and the at least one outer aperture opening.

Multi-channel fiber laser amplifier combining apparatus including integrated spectral beam combination and a tapered fiber bundle having multiple fiber outputs

Abstract: A fiber laser amplifier system including a plurality of master oscillators each generating a signal beam at a different wavelength. A splitter for each master oscillator splits the signal beam into a plurality of fiber beams to be separately amplified. A separate tapered fiber bundle receives the amplified beam for each master oscillator, where each tapered fiber bundle includes a plurality of input end fibers, a plurality of output end fibers and a center bundle portion, where each input end fiber is coupled to a separate one of the fiber amplifiers, where the bundle portion combines all of the fiber beams received by the input end fibers into a single combined beam and each output end fiber is capable of receiving the combined beam separately from the other output end fibers. A separate optical output channel receives one of the output end fibers from each tapered fiber bundle.

Method and system for simultaneously displaying Doppler image, B-type image and colored blood flow image

Abstract: The invention discloses a method and system for simultaneously displaying a Doppler image, a B-type image and a colored blood flow image. The method comprises the steps of: sending B-type scanning pulses and Doppler scanning pulses at an interval according to a time sequence; receiving ultrasonic echoes of the scanning pulses and converting into electric signals; carrying out B-type signal beam synthesis on B-type ultrasonic echoes, and carrying out Doppler signal beam synthesis on Doppler ultrasonic echoes; transmitting the signal obtained after the B-type signal beam synthesis to a B-type signal processing module to obtain B-type image data; dividing the signal obtained after the Doppler signal beam synthesis into two parts, carrying out Doppler signal processing on one part to obtain Doppler frequency spectrum data, and carrying out colored blood flow signal processing on the other part to obtain colored blood flow image data; and transmitting the B-type image data, Doppler frequency spectrum data and colored blood flow image data to a display module for synchronously displaying. The method and system disclosed by the invention have the advantages that: Doppler, B-type and colored blood flow images can be simultaneously displayed under the condition of not increasing extra emission.

Holographic 3d printing apparatus and method of driving the same

Abstract: A holographic three-dimensional (3D) printing apparatus and a method of driving the same are provided. The holographic 3D printing apparatus includes a light source configured to emit a beam, a beam splitting and expanding unit configured to split the emitted beam into a reference beam and a signal beam and expand the signal beam, an illumination unit configured to extract the expanded signal beam and collimate the extracted signal beam, a spatial light modulator (SLM) configured to modulate the collimated signal beam, an objective lens unit configured to emit the modulated signal beam to a holographic recording medium, and a reference beam forming unit configured to emit the reference beam to the holographic recording medium.

Two-dimensional confocal imaging using OCT light source and scan optics

Abstract: Various approaches are disclosed for simultaneously generating optical coherence tomography (OCT) and confocal scanning laser images by spatially separating the signal normally used for OCT imaging with selective reflecting or beam directing devices. In one preferred embodiment, the invention includes a mirror having a central transmission region, such that the radially outer region of the returning signal beam is reflected and used for generating a confocal image while the central part of the signal beam is transmitted and used to generate an OCT image. In other embodiments, the signals may be spatially separated in other ways, such as with an optic having a reflective center surface, a mirror having two parts oriented at different angles, one or more wedged optics, or a dispersive component. A further aspect of the invention is the ability to increase the frame rate of the confocal imaging.

Heterodyne modulation method for vibration detection

Abstract: The invention discloses a heterodyne modulation method for vibration detection, which comprises the steps that: 1, the incoming beam is split into two beams through a beam splitter, one beam is a reference beam, and the other beam is a signal beam; 2, the reference beam sequentially passes through an electrooptical modulator and a collimating lens to enter a beam splitter prism; the signal beam directly illuminates a vibration object through the beam splitter prism and an optical antenna, is reflected by the vibration object to be received by the optical antenna, and finally enters the beam splitter prism; 3, the reference beam which enters the beam splitter prism and the signal beam which is reflected by the vibration body to enter the beam splitter prism nterfere with each other, and then enter a photoelectric detector; and 4, the photoelectric detector receives the electric signal which carries the vibration signal of the object, so the heterodyne modulation of the incoming beam isrealized. Through utilizing the heterodyne modulation method, the problems of difficult later-period signal modulation, limited modulation method and the like which are caused by the high modulation frequency of an acoustic optical modulator are solved.

Signal amplification based on the local nonlinear Mach–Zehnder interferometer

Abstract: Using the phase modulation of spatial solitons, a new scheme for all-optical signal amplification has been proposed in this paper The considered structure is composed of the nonlinear Mach–Zehnder interferometer (NMZI) with the straight control waveguide (CWG), the uniform nonlinear medium (NLM) and the linear output waveguide The local NMZI functions like a phase shifter The light-induced index changes in the local nonlinear MZI are responsible for the input beam routing in the uniform nonlinear medium The coupling of the input beam to the output waveguide depends on its propagation direction in the NLM It is shown that the signal launched at CWG can deflect the beam launched at the NMZI (input beam) and a modulated (amplified) output could be obtained at the output waveguide Further, signal pulse may be reshaped by appropriately increasing the NLM length In addition, amplification factor may be enhanced by increasing the NLM length and injecting an appropriate continuous wave beam along with the signal beam at CWG

Multi channel detector, optics therefor and method of operating thereof

Abstract: A secondary charged particle detection device for detection of a signal beam is described. The device includes a detector arrangement having at least two detection elements with active detection areas, wherein the active detection areas are separated by a gap, a particle optics configured for separating the signal beam in a first portion of the signal beam and in at least one second portion of the signal beam, configured for focusing the first portion of the signal beam, and configured for deflecting and focusing the at least one second portion of the signal beam, wherein the particle optics includes a first electrode and at least one second electrode. Therein, the first electrode is an inner electrode and the at least one second electrode is provided radially outward of the first electrode.

Trapping polarization of light in nonlinear optical fibers: An ideal Raman polarizer

Abstract: The main subject of this contribution is the all-optical control over the state of polarization (SOP) of light, understood as the control over the SOP of a signal beam by the SOP of a pump beam. We will show how the possibility of such control arises naturally from a vectorial study of pump-probe Raman interactions in optical fibers. Most studies on the Raman effect in optical fibers assume a scalar model, which is only valid for high-PMD fibers (here, PMD stands for the polarization-mode dispersion). Modern technology enables manufacturing of low-PMD fibers, the description of which requires a full vectorial model. Within this model we gain full control over the SOP of the signal beam. In particular we show how the signal SOP is pulled towards and trapped by the pump SOP. The isotropic symmetry of the fiber is broken by the presence of the polarized pump. This trapping effect is used in experiments for the design of new nonlinear optical devices named Raman polarizers. Along with the property of improved signal amplification, these devices transform an arbitrary input SOP of the signal beam into one and the same SOP towards the output end. This output SOP is fully controlled by the SOP of the pump beam. We overview the sate-of-the-art of the subject and introduce the notion of an "ideal Raman polarizer".

Optical interferometer, data acquisition device, and data acquisition method

Abstract: An optical interferometer includes: a light source that emits a coherent first beam and a second beam that has a frequency difference corresponding to the natural frequency of a target molecule; amplitude modulating means that modulates the amplitude of the second beam; splitting means that splits the first beam into a reference beam and a first applied beam; optical path length adjusting means that adjusts the optical path length of the reference beam; and detecting means that detects an interference pattern between the reference beam and the first beam (a signal beam) that has experienced a stimulated Raman loss or gain in accordance with the amplitude modulation as a result of the frequency difference resonating with the target molecule when the first applied beam and a second applied beam (the amplitude modulated second beam) have been applied to a measurement position of an object.

Optical interferometer, information acquisition apparatus, and information acquisition method

Abstract: An optical interferometer includes: a light source that emits a coherent first beam and a second beam that has a frequency difference corresponding to the natural frequency of a target molecule; amplitude modulating means that modulates the amplitude of the second beam; splitting means that splits the first beam into a reference beam and a first applied beam; optical path length adjusting means that adjusts the optical path length of the reference beam; and detecting means that detects an interference pattern between the reference beam and the first beam (a signal beam) that has experienced a stimulated Raman loss or gain in accordance with the amplitude modulation as a result of the frequency difference resonating with the target molecule when the first applied beam and a second applied beam (the amplitude modulated second beam) have been applied to a measurement position of an object.

Coherent optical reception device and coherent optical reception method

Abstract: A coherent optical receiver involves complicated control processing in order to maintain good received signal qualities. Thus, the coherent optical receiver of the present invention has a coherent optical receiver for receiving an input signal beam; an input power monitoring unit for obtaining input power information that is defined on the basis of the power level of the input signal beam; a local oscillator that is connected to the coherent optical receiver; and a control unit that is connected to the coherent optical receiver, the input power monitoring unit, and the local oscillator. The coherent optical receiver is equipped with a 90° hybrid circuit, photoelectric converters, and amplifiers. The input power monitoring unit is placed inside the light path of the input signal beam and in a stage before the amplifiers. The control unit obtains the input power information from the input power monitoring unit and controls the power level of a locally oscillated beam output from the local oscillator on the basis of the input power information.

Localized dynamic light scattering system with doppler velocity measuring capability

Abstract: A localized dynamic light scattering measurement system includes a beam displacer for splitting an incident beam having two orthogonal linearly polarized beam components with slightly different frequencies into two orthogonal linearly polarized output beams focused onto an object to be measured. The beam displacer cooperates with an iris to collect and recombine scattering beams each reversely backscattered at 180 degrees from the object so as to form a signal beam, which is polarized by a polarizer to produce two polarization components, thereby generating a heterodyne interference signal associated with the polarization components. A signal processing unit obtains measurement data on the object based on power spectrum or autocorrelation data corresponding to the heterodyne interference signal.

Wavelength selective optical switch device and method of controlling characteristics thereof

Abstract: A wavelength selective optical switch device includes an incidence and exit part where a signal beam made of light of a multiplicity of wavelengths enters and a signal beam of a selected wavelength exits, a wavelength dispersion element that spatially disperses a signal beam according to the wavelength thereof and multiplexes reflected light, a condensing element that condenses the light dispersed by the wavelength dispersion element onto a two-dimensional plane, and a wavelength selection element that uses a multilevel optical phased array arranged in a position to receive incident light developed on an xy-plane made of an x-axis direction and a y-axis direction perpendicular thereto developed according to a wavelength, having a multiplicity of pixels arrayed in a lattice on the xy-plane, and that cyclically changes the phase shift amount in the y-axis direction to a sawtooth wave pattern for each pixel on the x-axis.

Heterodyne interferometer using aom

Abstract: PURPOSE: A heterodyne interferometer using an acoustic optical modulator is provided to simplify a structure of a whole system by using a single AOM(Acoustic Optical Modulator) and small numbers of optical systems because the AOM is constituted as a double-pass. CONSTITUTION: A heterodyne interferometer using an acoustic optical modulator comprises a light source(400), a polaroid beam splitter(410), an acoustic optical modulator(420), an AOM driving unit(430), a first mirror(450), a second mirror(454), a mirror driving unit, a QWP(Quarter-Wave Plate)(440), a photo-detector, and a demodulator(470). The polaroid beam splitter radiates or reflects irradiated light according to a polarization state. The acoustic optical modulator divides the light passed through a PBS(Polaroid Beam Splitter) and irradiated into a first ray and second ray which frequency is biased as much as a driving frequency(f_RF). The AOM driving unit drives the AOM by a driving frequency. The first mirror reflects the first ray again along an irradiation path of the first ray so that signal beam is offered. The second mirror reflects the second ray again along an irradiation path of the first ray so that reference beam is offered.

Optical information recording and reproducing device, optical information recording and reproducing method, and reproducing device

Abstract: In recording and reproducing devices that use angular-multiplexing holography, accessing a recorded hologram of interest had taken time because after positioning at the vicinity of the hologram, it had been necessary to carry out fine adjustment of the position while checking the signal quality of the hologram. The optical information recording and reproducing device according to the present invention uses angular-multiplexing to record interference patterns formed from a signal beam and a reference beam onto an optical information recording medium as page data and reproduces information from the optical information recording medium, said optical information recording and reproducing unit being provided with: a light-source unit that outputs light; an optical splitting unit that splits the light into a reference beam and a signal beam; an angle controlling unit that controls the angle for the direction of angle multiplexing at which the reference beam enters the optical information recording medium; an optical detecting unit that detects a reproduced image that is reproduced by using the reference light; and a position control unit that controls the position relationship between the reference beam and the optical information recording medium. The device treats a set of page data as a book, and during recording, at least a portion of the page data in adjacent books is recorded while the entrance angle for the direction of angular-multiplexing for the reference light is shifted by means of the angle controlling unit. During reproduction, at least a portion of the light amount of a reproduced image is detected by using the optical detecting unit, and the position of the book is detected on the basis of information about the detected light amount.

Polarization singularities in second harmonic beam generated from the surface of a medium with spatial dispersion of nonlinear response

Abstract: The conditions of appearance and the behavior of C-point-polarization singularities in the second harmonic beam reflected from the surface of an isotropic chiral medium with spatial dispersion of nonlinearity in the case of oblique incidence of the elliptically polarized Gaussian profile fundamental beam is considered. Within the framework of the paraxial approximation (first order approximation on the beam divergence angle) it is shown that for any medium parameters there is a polarization state of the incident beam which provides the appearance of the C-point in the center of the transverse section of second harmonic beam. Small variations of this polarization state with a constant value of the angle of incidence or small variations of the angle of incidence with a constant polarization state both result in a shift of the C-point out of the center of the signal beam. The beam structure transformation and symmetry breaking is studied when proceeding from the normal incidence geometry to the oblique one.

Apparatus and method for recording micro-hologram

Abstract: An apparatus and method for recording a micro-hologram are provided. The micro-hologram recording apparatus includes a first light source configured to emit a first light, the first light being coherent, a first optical system configured to divide the first light into a signal beam and a reference beam, and supply the signal beam and the reference beam to a location on a hologram recording medium, a second light source configured to emit a second light, the second light being incoherent and not interfering with the signal beam and the reference beam, and a second optical system configured to supply the second light to the same location as the signal beam and the reference beam on the hologram recording medium.

Communications security in multiple-antenna wireless networks

Abstract: A system enhances communications security in a wireless local area network (WLAN). The system includes a multiple antenna array arranged to transmit and receive signals; and a transmitter/receiver coupled to the multiple antenna array and configured to transmit and receive the signals. The transmitter/receiver includes a beamformer, which in turn includes a signal processor component that generates a signal beam for transmission to an intended user, and a blinding component that computes one or more blinding beams using only channel state information of the intended user. The blinding beams have a zero inter-user interference condition with the signal beam. The transmitter/receiver transmits the signal beam and the blinding beams simultaneously

Trapping Polarization of Light in Nonlinear Optical Fibers: An Ideal Raman Polarizer

Abstract: The main subject of this contribution is the all-optical control over the state of polarization (SOP) of light, understood as the control over the SOP of a signal beam by the SOP of a pump beam. We will show how the possibility of such control arises naturally from a vectorial study of pump-probe Raman interactions in optical fibers. Most studies on the Raman effect in optical fibers assume a scalar model, which is only valid for high-PMD fibers (here, PMD stands for the polarization-mode dispersion). Modern technology enables manufacturing of low-PMD fibers, the description of which requires a full vectorial model. Within this model we gain full control over the SOP of the signal beam. In particular we show how the signal SOP is pulled towards and trapped by the pump SOP. The isotropic symmetry of the fiber is broken by the presence of the polarized pump. This trapping effect is used in experiments for the design of new nonlinear optical devices named Raman polarizers. Along with the property of improved signal amplification, these devices transform an arbitrary input SOP of the signal beam into one and the same SOP towards the output end. This output SOP is fully controlled by the SOP of the pump beam. We overview the state-of-the-art of the subject and introduce the notion of an “ideal Raman polarizer.”

Optical information recording apparatus, optical information reproducing apparatus, optical information recording/reproducing apparatus, optical information recording method, optical information reproducing method and optical information recording/reproducing method

Abstract: The above-described problem can be solved by the following optical-information reproducing apparatus: An optical-information reproducing apparatus for reproducing a hologram storage medium into which an interference pattern is recorded as a hologram, the interference pattern being formed by causing a reference beam and a signal beam to interfere with each other, the optical-information reproducing apparatus, including an optical detector for detecting a reproduced beam, the reproduced beam being acquired by illuminating the recorded hologram with the reference beam, an optical element for generating a first reference beam and a second reference beam by branching the reference beam, a wavefront detector for detecting wavefront aberration of the reference beam by causing the first reference beam and the second reference beam to interfere with each other, and a wavefront compensator for compensating the wavefront of the reference beam, wherein the wavefront compensator is adjusted based on an output of the wavefront detector.

Apparatus and method for evaluating hologram image recording medium

Abstract: A method for evaluating a hologram image recording medium includes: recording continuously a plurality of fine holograms, each being the same in size as an element hologram, on a hologram image recording medium to be evaluated, using either one of a two-beam interference between a reference beam and a signal beam both being a plane wave and a two-beam interference between a reference beam being a plane wave and a signal beam being a spherical wave; reproducing a diffraction image by irradiating the recorded fine hologram with a plane wave; from intensity distribution data based on a captured diffraction image, determining an intensity distribution data array and a diffracted beam intensity I s , the intensity distribution data array having the same shape and size as those of the fine hologram; and when the diffracted beam intensity I s takes on the maximum value I s ( max ), determining an SN ratio.

Near field broadband PIC processor with improved interference beam

Abstract: A Postbeamformer Interference Canceler (PIC) processes the signals derived from an array of antennas by forming two beams, a signal beam and an interference beam. This paper presents a method to study the performance of the PIC processor using the improved interference beam (IIB) for near field broadband directional sources. The technique presented in this paper extends the idea of previously published paper for far field beamforming to near field broadband beamforming and does not require the steering delays. A number of examples presented show the effectiveness, performance and capability of distance discrimination and robustness of the proposed broadband beamformer and compare with that using PIC with conventional interference beam (CIB) and with that using optimal element space processor (ESP).

Optical receiver and control method for optical receiver

Abstract: To limit the generation of symbol errors during signal detection by an optical receiver in a wide input range of signal beam strength using a simple configuration, the optical receiver is equipped with a local light emission and oscillating means for generating local oscillated light of a constant strength, an optical mixing means for mixing the local oscillated light and a first signal light and outputting the mixed light as a second signal light, a light receiving means for converting the second signal light to an electrical signal and outputting the electric signal as a first electric signal, an amplifying means for amplifying the first electric signal by a predetermined gain and outputting the amplified first electric signal as a second electric signal, and a signal processing circuit for processing the second electric signal, the gain being set so that the amplitude of the second electric signal falls within a permitted amplitude range in the input of the signal processing circuit.