Showing papers on "Signal beam published in 2010"

Solid-state ultrafast all-optical streak camera enabling high-dynamic-range picosecond recording.

Abstract: We demonstrate an ultrafast optical recording system based on a novel optical beam deflection technique. An optical pump temporarily creates an array of prisms that deflect an optical signal beam within a GaAs/AlGaAs planar waveguide. The fabricated device yielded, to our knowledge, the fastest sustained optical deflection reported to date and was used to create spatial representations of ultrafast temporal waveforms. A conventional camera was then used to record single-shot waveforms with a 2.5 ps resolution over a 50 ps record with a dynamic range in excess of 3000:1. Through further development, this all-optical streak camera could provide insight into previously unmeasurable phenomena in many fields.

Investigation of two-beam-pumped noncollinear optical parametric chirped-pulse amplification for the generation of few-cycle light pulses

Abstract: We demonstrate a new and compact ϕ-plane-pumped non-collinear optical parametric chirped-pulse amplification (NOPCPA) scheme for broadband pulse amplification, which is based on two-beam-pumping (TBP) at 532 nm. We employ type-I phase-matching in a 5 mm long BBO crystal with moderate pump intensities to preserve the temporal pulse contrast. Amplification and compression of the signal pulse from 675 nm - 970 nm is demonstrated, which results in the generation of 7.1-fs light pulses containing 0.35 mJ energy. In this context, we investigate the pump-to-signal energy conversion efficiency for TBP-NOPCPA and outline details for few-cycle pulse characterization. Furthermore, it is verified, that the interference at the intersection of the two pump beams does not degrade the signal beam spatial profile. It is theoretically shown that the accumulated OPA phase partially compensates for wave-vector mismatch and leads to extended broadband amplification. The experimental outcome is supported by numerical split-step simulations of the parametric signal gain, including pump depletion and parametric fluorescence.

Optical transmission system

Abstract: PROBLEM TO BE SOLVED: To set up an optical amplifier by determining an accurate gain even when an optical loss medium having loss characteristics, which are not uniform in a wavelength direction, is disposed on a pre-stage of the optical amplifier. SOLUTION: A controller 23 recognizes a noise light loss value, which indicates a loss that noise light output from an upstream-side optical amplifier 11 undergoes during propagation to a downstream-side optical amplifier 22 through an optical loss medium 21, and a signal beam loss value, which indicates a loss that a signal beam output from the upstream-side optical amplifier 11 undergoes during propagation to the downstream-side optical amplifier 22 through the optical loss medium 21, determines a loss difference which is a difference between the noise light loss value and the signal beam loss value and, when the downstream-side optical amplifier 22 is set up, decides the gain by performing compensation using the loss difference. COPYRIGHT: (C)2010,JPO&INPIT

Complete nonlinear polarization control in an optical fiber system.

Abstract: We consider the counterpropagating interaction of a signal and a pump beam in an isotropic optical fiber. On the basis of recently developed mathematical techniques, we show that an arbitrary state of polarization of the signal beam can be converted into any other desired state of polarization. On the other hand, an unpolarized signal beam may be repolarized into two specific states of polarization, without loss of energy. Both processes of repolarization and polarization conversion may be controlled by adjusting the polarization state of the backward pump.

Optical phase processing in a scattering medium

Abstract: An optical phase processing system for a scattering medium. A first beam has a direction and a wavefront and the first beam is configured to enter a holographic recording medium. A scattering medium is illuminated by a signal beam generating at least one scattered beam. An interference pattern is recorded from the at least one scattered beam and the first beam. A second beam is generated in a direction opposite to the direction of the first beam, the second beam having a wavefront and a phase substantially opposite to a phase of the wavefront of the first beam, and the second beam is configured to enter the holographic recording medium. The second beam and the interference pattern interact to generate at least one reconstructed beam having a phase substantially opposite to a phase of the at least one scattered beam, and the at least one reconstructed beam is configured to be viewable through the scattering medium.

Theoretical study of polarization attraction in high-birefringence and spun fibers.

Abstract: Lossless polarizers are conservative nonlinear optical devices that transform unpolarized light into highly polarized light without polarization-dependent losses. The device proposed here consists of an up to 100-m-long segment of nonlinear highly birefringent or unidirectionally spun fiber pumped from the output end by an intense backward-propagating beam. An initially unpolarized (scrambled) signal beam acquires a degree of polarization close to 100% toward the fiber output.

High repetition rate mid-infrared generation with singly resonant optical parametric oscillator using multi-grating periodically poled MgO:LiNbO3

Abstract: A high repetition rate mid-infrared singly resonant optical parametric oscillator (OPO) using MgO-doped multi-grating periodically poled LiNbO3 (MgO:PPLN) is demonstrated. A 1064 nm Q-switched Nd:YVO4 laser at 10 kHz repetition rate and pulse width of 17.8 ns was used to pump the OPO. The period of the quasi-phase matched (QPM) grating in the multi-grating MgO:PPLN chip varied from 25.5 to 31.5 μm in steps of 0.5 μm. This corresponds to the generation of a signal beam from 1.37 to 1.64 μm and an idler beam from 3.0 to 4.8 μm, respectively. A maximum signal power of 250 mW and idler power of 140 mW has been obtained with an input pump beam of power 1.92 W, for a grating period of 30.5 μm. A maximum optic–optic conversion efficiency of 20% and 7.4% in the idler has been observed. It has been observed that the output power increases as the period of the grating increases.

Note: An ultranarrow bandpass filter system for single-photon experiments in quantum optics

Abstract: We describe a combined ultranarrow bandpass filtering setup for single-photon experiments in quantum optics. The filter is particularly suitable for single-photon electromagnetically induced transparency (EIT) experiments, but can also be used in several similar applications. A multipass planar Fabry–Perot etalon together with polarization filters and spatial filtering allows 114 dB pump beam suppression, while the signal beam is attenuated by just 4 dB, although both wavelengths are only separated by 0.025 nm (9.2 GHz). The multipass etalon alone accounts for 46 dB suppression while it has a peak transmission of 65%. We demonstrate EIT experiments in Cs vapor at room temperature with probe power in the femtowatt regime using this filter.

Effect of resonator length on ZnGeP2 doubly resonant optical parametric oscillator pumped by a Tm,Ho:GdVO4 laser

Abstract: The effect of resonator length on ZnGeP2 doubly resonant optical parametric oscillator was reported in this letter. With the employment of a Tm,Ho:GdVO4 laser as the pump source at 2.05 μm, we have found that there are obvious peaks of the output power when the resonator lengths are matched to the length of the pump source. The ZGP OPO can generate a maximum output power of 4.27 W at 3.80 μm signal and 4.45 μm idler when the resonator length matches that of the pump source.

Narrow-bandwidth tunable picosecond pulses in the visible produced by noncollinear optical parametric amplification with a chirped blue pump

Abstract: Narrow-bandwidth (~27 cm−1) tunable picosecond pulses from 480 nm-780 nm were generated from the output of a 1 kHz femtosecond titanium:sapphire laser system using a type I noncollinear optical parametric amplifier (NOPA) with chirped second-harmonic generation (SHG) pumping Unlike a femtosecond NOPA, this system utilizes a broadband pump beam, the chirped 400 nm SHG of the Ti:sapphire fundamental, to amplify a monochromatic signal beam (spectrally-filtered output of a type II collinear OPA) Optimum geometric conditions for simultaneous phase- and group-velocity matching were calculated in the visible spectrum This design is an efficient and simple method for generating tunable visible picosecond pulses that are synchronized to the femtosecond pulses

All-optical switching of dark states in nonlinear coupled microring resonators.

Abstract: We propose and analyze an on-chip all-optical dynamic tuning scheme for coupled nonlinear resonators employing a single control beam injected in parallel with a signal beam. We show that the nonlinear Kerr response can be used to dynamically switch the spectral properties between a “dark state” and electromagnetically induced transparency configurations. Such a scheme can be realized in integrated optical applications for pulse trapping and delaying.

Oscillation dependence of two-wave mixing gain for unidirectional ring resonator in photorefractive materials

Abstract: Dependence of the coupling strength of two-wave mixing gain in photorefractive materials for the single unidirectional ring resonator on oscillation conditions has been analyzed in the strong nonlinear regime. In this regime, difference between the frequency of the pump beam and oscillating beam is proportional to the cavity-length detuning, which can be explained in terms of the photorefractive phase-shift. This phase-shift results due to slightly non-degenerate two-wave mixing that compensates for cavity detuning and satisfies the round-trip phase condition for the steady-state oscillation. The presence of such a phase-shift allows the possibility of the nonreciprocal steady-state energy transfer between the pump and oscillating beams. If the gain due to the beam coupling is large enough to overcome the cavity losses then the signal beam is amplified in the presence of material absorption. Such amplification is responsible for the oscillations. For the single unidirectional ring resonator, the effects of cavity-length detuning, energy coupling coefficient, crystal thickness of the material, reflectivity of the cavity mirrors and material's absorption coefficient on the frequency and intensity of oscillations have also been studied in detail. It has been found that for the smaller value of absorption coefficient ( α ) of the photorefractive crystal, the unidirectional ring resonator can oscillate at almost any cavity-length detuning (Δ Γ ) whereas for the larger value of α oscillation occurs only when the cavity-length detuning is limited to small region (around Δ Γ =0). But reverse of the case is found for energy coupling coefficient ( γ 0 ).

All-optical switching of dark states in nonlinear coupled microring resonators

Abstract: We propose and analyze an on-chip all-optical dynamical tuning scheme for coupled nonlinear resonators employing a single control beam injected in parallel with a signal beam We show that nonlinear Kerr response can be used to dynamically switch the spectral properties between "dark-state" and electromagnetically-induced transparency configurations Such scheme can be realized in integrated optical applications for pulse trapping and delaying

Effect of photoconductivity and dielectric constant of the photorefractive materials on two-beam coupling gain and phase-shifts for a single unidirectional photorefractive ring resonator

Abstract: Photoconductive dependence of two-beam coupling between the pump beam and the signal beam in photorefractive materials have been analyzed in case of non-degenerate wave mixing under the undepleted pump approximation method. During the two-wave mixing in photorefractive materials, steady state amplification of the signal beam and oscillation characteristics of a single unidirectional ring resonator has been studied. The domination of the two-beam coupling gain over the combined absorption and resonator losses such as Fresnel reflections from the crystal and imperfect mirrors builds up unidirectional oscillation. The buildup of such an oscillation leads to a saturation of the gain, which can be explained in terms of the photorefractive phase-shift. The existence of this phase-shift between the photorefractive index grating and the illumination intensity pattern, which is of characteristic of the photorefractive effect, leads to an energy transfer between the two beams. For a single unidirectional ring resonators, the effects of photoconductivity of the materials, two-beam energy coupling coefficient, dielectric constant, crystal thickness, and material's absorption coefficient on amplification of the two-beam coupling gain and photorefractive phase-shifts of the signal beam have also been studied in detail. It has been found that amplification of the signal beam and phase-shift can be enhanced by taking the photorefractive crystal having higher photoconductivity and lower dielectric constant, which improves performance of the resonators.

Minimization of the fluctuation in the signal beam intensity of a nonlinear optical medium with a transmission grating

Abstract: Fluctuation in the intensity of the output signal beam of a photorefractive optical resonator can be reduced significantly by employing pump beam positive feedback. The fractional intensity transfer which is independent of time in the absence of fluctuation becomes time dependent in the presence of fluctuation of the optical wave-mixing process. The influence of various controlling parameters on the relative fluctuation of the output signal intensity has also been studied.

Switchable hybrid receiver for coherent and direct optical detection

Abstract: Embodiments of the present invention provide a switchable dual-mode detection system that can be electronically or optically switched between direct and coherent detection. The dual-mode detection system comprises a photo detector and one or more switching elements used in conjunction with the photo detector to electronically or optically switch the detection system between direct and coherent detection. The switching elements may include a switchable detector driver that selectively biases the photo detector into a low gain mode for coherent detection and a high gain mode for direct detection, and/or a switchable optical subsystem that selectively mixes a local oscillator beam with the input signal beam for coherent detection and not for direct detection, and/or an amplifier switch that selectively directs the output photo current of the photo detector to one of two amplifiers, where one of the amplifiers is optimized for direct detection and the other for coherent detection.

Method and apparatus for reading from a near-field optical recording medium, and near-field lens for the apparatus

Abstract: The present invention relates to a method and an apparatus (1) for reading from a near-field optical recording medium. The apparatus (1) includes: - an optical system (2, 33) for generating a signal beam (3') and a reference beam (3"); - a near-field lens (9b) for illuminating the signal beam (3') onto the near-field optical recording medium (10), for collimating a reflected signal beam (40), and for reflecting the reference beam (3"); and - at least a first detector (25-1) and a second detector (45-1) for obtaining a homodyne detection signal from the reflected signal beam (40) and the reflected reference beam (3").

Fiber amplifying system i.e. high-power fiber laser amplifier, for use in e.g. industrial application, has end plate expanding output beam of fiber bundle, and beam sampler sampling part of output beam of plate and generating sampled beam

Abstract: The system (10) has a main oscillator (12) generating a signal beam (14), and a beam splitter dividing the signal beam into a set of fiber beams. A tapered fiber bundle (72) is provided with inlet and outlet ends, where the inlet end is connected with the outlet end. The tapered fiber bundle delivers an output beam, and an end plate (74) is optically connected with the outlet end of the tapered fiber bundle. The end plate expands the output beam of the tapered fiber bundle, and a beam sampler (82) samples a part of the output beam of the end plate, and generates a sampled beam.

Holographic Read-Only Memory Fabricated by Deposition of Reflector after Writing Process with Aromatic Photopolymer Recording Layer

Abstract: The deposition of reflector after writing (DRAW) process has been proposed for the fabrication of reflective-type holographic read-only memories. In the DRAW process, a reflector is deposited on a recording medium after signal writing, resulting in the reduction of noise holograms written by reflected beams from a reflector in the write process. Significant improvements are experimentally confirmed in read and write (R/W) performances in DRAW-processed holographic media. The combination of the DRAW process and an aromatic photopolymer recording material realizes low noise, high signal-to-noise ratio, and low symbol error rate characteristics at large multiplexing numbers up to 1020. In conventional reflective-type holographic media, ghost noise is superimposed on the readout signal, causing deterioration in R/W characteristics. The wave vector analyses clarify the mechanism by which the noise holograms are written and ghost noise is superimposed on the signal beam in the conventional media.

Tunneling of optical beams through inhomogeneity of a refractive index

Abstract: We consider the effect of tunneling of optical beams through a narrow induced inhomogeneity in a refractive index. It is shown that under the condition of total internal reflection from the induced channel, part of the signal beam leaks if the channel is narrow. Dependence of the pump beam width at which the tunneling of half signal power occurs is found as a function of the pump intensity and the angle of beam crossing.

Systems, methods, devices, and computer readable media for terahertz radiation detection

Abstract: Systems, devices, methods, and computer-readable media relating to terahertz radiation detection are disclosed. A method of detecting terahertz radiation may include transmitting a reference beam and a signal beam through a common-path interferometer. The method may further include transmitting a terahertz beam through a target object. Furthermore, the method may include causing the signal beam and the terahertz beam to simultaneously propagate through an electro-optical element within the common-path interferometer after transmitting the terahertz beam through the target object to induce a phase delay between the signal beam and the reference beam. In addition, the method may include calculating the phase delay and calculating an amplitude of an electric field of the terahertz beam from the phase delay.

Systems and methods for quantum illumination detection for optical communications and target detection

Abstract: A detection system including a receiver, a transmitter, and a processor for stealthy target detection or optical communications is described. Optical communications may be spread spectrum encoded communications over a bright background communication channel. The transmitter includes a quantum frequency entanglement source for outputting a signal beam and an idler beam, and transmission optics for directing the signal beam towards a remote surface. Photons in the idler beam are quantum-mechanically entangled in frequency with photons the signal beam. The transmitter includes a first spectrometer for measuring a frequency band associated with photons in the idler beam. The receiver includes a second spectrometer for identifying the frequency band associated with the photons in the received return beam. The system includes a processor configured to process the output of the spectrometers to determine the presence of a target in a target region or a message encoded in the received return beam.

A high Brillouin amplification using liquid fluorocarbon

Abstract: Although the gain coefficient of the Stimulated Brillouin Scattering (SBS) of the fluorocarbon liquid C 8 F 18 is substantially lower than for other nonlinear media, it is an attractive medium since its highly purified version has a high optical breakdown threshold, and it is stable and very safe to operate. We have utilized it as a phase conjugate mirror (PCM) and the PCM reflectivity better than 90% has been achieved at optimized focusing conditions of an incoming beam. The output energy of the phase conjugated pulse linearly followed the input pulse energy after reaching the threshold level at about 3.3 mJ. The slope efficiency was estimated about 95% without taking into account components' losses. Brillouin amplification through SBS has been realized in highly purified fluorocarbon liquid C 8 F 18 . This report discusses the design and results of performed experimental studies of the SBS in C 8 F 18 demonstrating the amplification of a week signal beam (37 nJ) reaching up to 10 5 or 50 dB.

Nonlinear diffraction and total internal reflection in optical-beam interaction in defocusing media

Abstract: We elaborate the theory of reflection of an optical signal beam from an inhomogeneous channel created by a high-power laser beam of different frequency in a nonlinear defocusing medium. We study the effects of total internal reflection and nonlinear diffraction in the interaction of these beams. We derive and analyze the equation for the trajectory of the reflected signal beam and obtain the expression for the critical value of beam-intersection angle below which the total internal reflection occurs. We discuss the results of numerical modeling of nonlinear Schr¨odinger equations for envelopes of the beams in media with quadratic, photorefractive, and thermal nonlinearities. We present experimental data on the interaction of beams of argon and helium–neon lasers in a cuvette with tinted alcohol.

Photonic crystal switches based on nonlinear directional couplers

Abstract: In this paper, the all optical switch based on nonlinear photonic crystal directional coupler in both, hexagonal and square lattice structure has been simulated and analyzed by the finite difference time domain (FDTD) method. The refractive index of the nonlinear central row of the coupler is increased by the pump signal. Hence, it works in the nonlinear state and the light is guided to the cross output. We have tried to reduce the required power for switching and increase the coupling efficiency by modifying the bends structure in the directional coupler which is implemented in square lattice. Therefore, the input signal beam can be controlled to be exchanged between two output ports to earn the highest output power ratio and the smallest amount of power required for nonlinear performance.

Sliding beam converging synthetic aperture laser imaging radar

Abstract: A sliding spotlight laser-imaging SAR is characterized in that the sliding spotlight laser-imaging SAR comprises a laser-imaging SAR which is composed of an optical emission system and an optical receiving system; the optical receiving system is provided with a mechanism used for eliminating echo wave face aberration and the optical emission system is provided with a phase quadratic-term biasing mechanism controlled by lighting facula; the laser-imaging SAR moves in a straight line and the optical emission system emits an emission signal beam with a certain divergency during the moving to form an optical track with a certain diameter on the plane of a measured object and the focused imaging zone in the plane of the measured object is scanned by the optical track at a slow speed; the emission signal beam and a heterodyne receiving FOV are concentric and the beam divergency is equal to the angle of the heterodyne receiving FOV.

Apparatus and method for detecting signal beam

Abstract: A signal-light detection apparatus includes a polarization extractor that extracts a polarization component that is substantially in parallel with a specified axial direction from an input light, a polarization rotator that changes a relative angle between a direction of polarization of the input light and an axial direction of the polarization extractor, a photodetector that detects an optical power of the polarization component extracted by the polarization extractor, and a determination device that determines whether the input light includes a signal component, based on a variation in the optical power detected by the photodetector.