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Showing papers on "Phase conjugation published in 2008"


Journal ArticleDOI
TL;DR: The receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation is shown.
Abstract: Coherent optical OFDM (CO-OFDM) has recently been proposed and the proof-of-concept transmission experiments have shown its extreme robustness against chromatic dispersion and polarization mode dispersion. In this paper, we first review the theoretical fundamentals for CO-OFDM and its channel model in a 2x2 MIMO-OFDM representation. We then present various design choices for CO-OFDM systems and perform the nonlinearity analysis for RF-to-optical up-converter. We also show the receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation.

719 citations


Book ChapterDOI
01 Jan 2008
TL;DR: In this paper, a review of all-optical nonlinear signal processing devices that relate to both chalcogenide glasses and highly nonlinear fibers using both phase and non-phase-matched processes is presented.
Abstract: Publisher Summary This chapter reviews all-optical nonlinear signal processing devices that relate to both chalcogenide glasses and highly nonlinear fibers, using both phase- and nonphase-matched processes. Nonphase-matched processes do not rely on critical matching of waveguide refractive indices between incoming and outgoing signals. Phase-matched processes are best represented by optical parametric signal processing techniques. Approaches based on highly nonlinear silica fiber as well as chalcogenide-glass-based fiber and waveguide devices are discussed. A contrast is made between two qualitatively different approaches to all-optical signal processing based on non-phase-matched and phase-matched processes. All-optical signal processing devices are steadily coming of age, and the prospect for reducing peak power requirements of PLC-based all-optical circuits below the current levels of a few watts to tens of milliwatts or even lower will go a long way to ensure that all-optical nonlinear devices will play an integral part in future telecommunications systems. All-optical applications of 2R and 3R regeneration, wavelength conversion, parametric amplification, phase conjugation, delay, performance monitoring, and switching are briefly reviewed.

50 citations


Journal ArticleDOI
TL;DR: In this article, a steady-state model for Brillouin and Raman backscatter from an inhomogeneous plasma is presented, where the daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive.
Abstract: A one-dimensional, steady-state model for Brillouin and Raman backscatter from an inhomogeneous plasma is presented. The daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung damping, bremsstrahlung emission, Thomson scattering off density fluctuations, and whole-beam focusing are included. The numerical code DEPLETE, which implements this model, is described. The model is compared with traditional linear gain calculations, as well as “plane-wave” simulations with the paraxial propagation code PF3D. Comparisons with Brillouin-scattering experiments at the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] show that laser speckles greatly enhance the reflectivity over the DEPLETE results. An approximate upper bound on this enhancement, motivated by phase conjugation, is given by doubling the DEPLETE coupling coefficient. Analysis with DEPLETE of an ign...

48 citations


Journal ArticleDOI
TL;DR: A technique for generating large, all-optical delays while simultaneously minimizing pulse distortion by using temporal phase conjugation via four-wave mixing in Si nanowaveguides is demonstrated.
Abstract: We demonstrate a technique for generating large, all-optical delays while simultaneously minimizing pulse distortion by using temporal phase conjugation via four-wave mixing in Si nanowaveguides. Using this scheme, we achieve continuously tunable delays over a range of 243 ns for 10 Gb/s NRZ data.

48 citations


Journal ArticleDOI
TL;DR: An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given in this paper, based on the results of the second International Workshop on Optical Phase Conjugation (OPC) held in Potsdam/Germany in 2007.
Abstract: An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given. This report is based on the results of the “Second International Workshop on stimulated Brillouin scattering and phase conjugation” held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

42 citations


Patent
28 Oct 2008
TL;DR: In this article, a two-pump optical parametric device (OPD) having a nonlinear birefringent fiber, in which various four-wave mixing (FWM) processes can occur, is presented.
Abstract: A two-pump optical parametric device (OPD) having a nonlinear birefringent fiber, in which various four-wave mixing (FWM) processes can occur. The OPD applies, to the nonlinear birefringent fiber, two pump waves, each polarized at about 45 degrees with respect to a birefringence axis of the fiber, and a polarized input signal. A relevant FWM process couples the pump waves and the signal to cause the fiber to generate a desired output signal. In one configuration, the relevant FWM process is inverse modulational interaction, which causes the desired output signal to be generated through amplification or attenuation of the input signal. In another configuration, the relevant FWM process is phase conjugation, which causes the desired output signal to be generated through amplification of the input signal. In yet another configuration, the relevant FWM process is Bragg scattering, which causes the desired output signal to be generated as a corresponding idler signal.

20 citations


Journal ArticleDOI
TL;DR: The implementation of a secure optical system using fully phase encryption is described, and a lithium niobate crystal has been used as a phase contrast filter to change the decrypted phase image into an amplitude image, thus alleviating the need for alignment of the phase contrast set up in the Fourier plane.
Abstract: In this paper, the implementation of a secure optical system using fully phase encryption is described. A two-dimensional phase image obtained from an amplitude image is encrypted and decrypted by using a spatial light modulator working in phase mode. The fully phase encryption is achieved using double random phase encoding. The encrypted image is holographically recorded in a photorefractive crystal and is then decrypted by generating, through phase conjugation, the conjugate of the encrypted image. A lithium niobate crystal has been used as a phase contrast filter to change the decrypted phase image into an amplitude image, thus alleviating the need for alignment of the phase contrast set-up in the Fourier plane. Simulation results are provided to verify the proposed study. The mean square error between the primary image and decrypted image has been calculated to study the sensitivity of the system.

17 citations


Journal ArticleDOI
TL;DR: In this article, 11 invited and 37 contributed papers focus on nonlinear-optical signal processing, including nonlinear pulse shaping, 2R and 3R regeneration, optical clock recovery, optical limiting, optical bistability, optical switching/gating, optical data format conversion, wavelength conversion, phase conjugation, phase-sensitive amplification, optical delay lines, optical burst/packet switching, alloptical OTDM multiplexing/demultiplexing, and micro-and nano-scale nonlinear optical devices.
Abstract: The 11 invited and 37 contributed papers in this special issue focus on nonlinear-optical signal processing. Topics covered include: nonlinear pulse shaping; 2R and 3R regeneration; all-optical clock recovery; optical limiting; optical bistability; all-optical switching/gating; optical data format conversion; wavelength conversion; phase conjugation; phase-sensitive amplification; optical delay lines; optical burst/packet switching; all-optical OTDM multiplexing/demultiplexing; and micro- and nano-scale nonlinear-optical devices.

16 citations


Journal ArticleDOI
TL;DR: The dynamic properties of two-photon pumped blue lasing (similar to 470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by similar to 160-fs laser pul...
Abstract: The dynamic properties of two-photon pumped blue lasing (similar to 470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by similar to 160-fs laser pul ...

11 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed a theoretical model to study optical phase conjugation via stimulated Brillouin scattering (OPC-SBS) in narrow band gap transversely magnetized semiconductors.

11 citations


Journal ArticleDOI
TL;DR: Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length, finding that fidelity remains high over much longer fiber lengths than previous models calculated.
Abstract: Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length. A phase conjugate fidelity over 80% was measured from SBS in a 40 m fiber using a pinhole technique. Fidelity decreases with fiber length, and a fiber with a numerical aperture (NA) of 0.06 was found to generate good phase conjugation fidelity over longer lengths than a fiber with 0.13 NA. Modeling and experiment support previous work showing the maximum interaction length which yields a high fidelity phase conjugate beam is inversely proportional to the fiber NA2, but find that fidelity remains high over much longer fiber lengths than previous models calculated. Conditions for SBS beam cleanup in step-index fibers are discussed.

Journal ArticleDOI
TL;DR: In this article, the output signal and idler pulses generated by dispersion-shifted-fiber-based four-wave mixing (FWM) with pulsed signal input are analyzed.
Abstract: The output signal and idler pulses generated by dispersion-shifted-fiber-based four-wave mixing (FWM) with pulsed signal input are analyzed. A set of analytical expressions for the amplitude and phase of the output pulses is derived. Analytical analysis shows that the generated idler pulse is far away from the phase conjugation of the input signal, and that the output signal is not an amplified replica of the input signal. These phenomena are due to both the phase distortion caused by self- and cross-phase modulation and the temporal envelope broadening resulting from pump depletion. Besides, in the frequency domain, the spectral inversion between signal/idler will be destroyed. The implications of the phase and shape distortions in all-optical signal processing by FWM are discussed. The induced phase distortions of idler pulses in dual pumps case are found to be much smaller than those of the single-pump case.

Journal ArticleDOI
TL;DR: In this paper, the multiphoton wave function after the Kerr interaction was obtained analytically for an arbitrary photon number and the nonlinear effects appearing in this wave function were evaluated quantitatively, revealing the limitations of nonlinear quantum optics theories based on single-mode approximations.
Abstract: The multiphoton wave function after Kerr interaction is obtained analytically for an arbitrary photon number. The wave function is composed of two fundamental functions: the input mode function and the linear response function. The nonlinear effects appearing in this wave function are evaluated quantitatively, revealing the limitations of nonlinear quantum optics theories based on single-mode approximations.

Patent
26 Mar 2008
TL;DR: In this paper, a detection device includes a pseudo sound source and a monitoring unit, which generates a scanning sound wave of a phase-conjugate wave in the time domain based on an acoustic signal by performing active phase conjugation.
Abstract: An object is detected without being constrained by the positional relationship between the object and the detecting position. A detection device includes a pseudo sound source and a monitoring unit. The pseudo sound source generates a scanning sound wave of a phase-conjugate wave in the time domain based on an acoustic signal by performing active phase conjugation, and causes the scanning sound wave to converge on the detection object from the above thereof within the propagation space by utilizing a feature that the scanning sound wave converges on the pseudo sound source which is the generation source of the acoustic signal. The monitoring unit extracts a reflected sound wave which is reflected at the detection object from the sound wave in the propagation space by performing passive phase conjugation. The detection object is detected based on presence or absence of the extracted reflected wave.

Journal ArticleDOI
TL;DR: In this article, the authors apply a selective phase conjugation of the second harmonic of a focused ultrasonic wave to diagnosing inhomogeneity of the nonlinear parameter in an acoustic medium.
Abstract: The principle of applying a selective phase conjugation of the second harmonic of a focused ultrasonic wave to diagnosing inhomogeneity of the nonlinear parameter in an acoustic medium is considered A solution to the three-dimensional problem of harmonic generation by phase-conjugated waves in a nonlinear medium with a localized isoechogenous inclusion is obtained The signal amplitudes detected by a transmitting-receiving transducer at the second and forth harmonics of a probe wave are calculated for varying position of the inclusion relative to the focus

Proceedings ArticleDOI
19 May 2008
TL;DR: This paper analyzes a modulation scheme and associated receiver algorithms that take advantage of the time reversal (phase conjugation) and properties of spread spectrum sequences known as Gold sequences and shows that this approach can give almost zero BER for a 2-hop communication compared to single hop.
Abstract: Underwater acoustic sensor networks (UASNs) consist of sensors that are deployed to perform collaborative monitoring of tasks over a given volume of water. The quality of the underwater acoustic link is highly unpredictable, since it mainly depends on fading and multipath, which are not easily modeled phenomena. This is return severely degrades the performance at higher layers such as extremely long and variable propagation delays. In addition, this variation is generally larger in horizontal links than in vertical ones. In this paper, we analyze a modulation scheme and associated receiver algorithms. This receiver design take advantage of the time reversal (phase conjugation) and properties of spread spectrum sequences known as Gold sequences. This technique improves the signal-to-noise ratio (SNR) at the receiver and reduces the bit error rate (BER). We then applied the phase conjugation to the case of network communication. We show that this approach can give almost zero BER for a 2-hop communication compared to single hop. This link layer information can be used at the network layer to formalize routing decisions. We show these improvements by means of analytical analysis and simulations.

Journal ArticleDOI
TL;DR: In this article, the reduction of nonlinear phase noise by use of Wiener filtering is studied, and it is shown that higher absolute dispersion can decrease signal fluctuation due to nonlinear noise, as well.
Abstract: As a parametric amplified noise, nonlinear phase noise limits the channel capacity in multispan fiber-optics transmissions. In this paper, the reduction of nonlinear phase noise by use of Wiener filtering is studied. Extracting signal from time-domain concepts, parametric amplified noise covering signal spectrum in frequency domain can be suppressed considerably. Timing jitter and ghost pulses due to intrachannel nonlinearities can also be compensated. Nonparametric Wiener filtering is used at the end of six configurations of dispersion compensation (DC) transmission lines: pre- and postlumped DC, distributed DC without optical phase conjugation (OPC), dispersion inversion (DI) about midlink OPC with, respectively, one-for-multispan, single type span and alternate type span on each side of OPC. It is found that single-DI and alternate-DI schemes have higher input power capacity than one-for-multi-DI scheme. Further reductions in the nonlinear phase noise accumulation for all these DC maps are obtained with Wiener filtering, and higher absolute dispersion can decrease signal fluctuation due to nonlinear phase noise, as well.

Proceedings ArticleDOI
29 May 2008
TL;DR: In this article, the use of a laser amplifier as a Degenerate Four-Wave Mixing (DFWM) element for phase conjugation is discussed. And the first demonstration of DFWM in a XeCl amplifier is presented.
Abstract: The use of a laser amplifier as a Degenerate Four‐Wave Mixing (DFWM) element for phase conjugation is a powerful general technique, particularly useful for UV excimer lasers In this paper we will discuss our initial experiments, which yielded the first demonstration of DFWM in a XeCl amplifier

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate wide-field real-time and depth-resolved holographic imaging of various reflecting objects using the all-optical phase coherent photorefractive effect in ZnSe quantum wells.
Abstract: We demonstrate wide-field real-time, and depth-resolved holographic imaging of various reflecting objects using the all-optical phase coherent photorefractive effect in ZnSe quantum wells. In contrast to current photorefractive quantum well devices, these devices use the coherence of excitons as a basis for holography. This has the advantage that the entire depth-resolved information of the object can be obtained from the brightness profile of the holographic image with a resolution of a few micrometers. In addition, the high diffraction efficiency and short refresh time of the phase coherent photorefractive effect allow high-speed video acquisition of moving objects.

Journal ArticleDOI
TL;DR: A continuous-wave beam was wavefront-split by a prism and propagated through separate paths before being coupled into a long, graded-index fiber and it was found that Stimulated Brillouin scattering did not conjugate the phase of the pump.
Abstract: A continuous-wave beam was wavefront-split by a prism and propagated through separate paths before being coupled into a long, graded-index fiber. Stimulated Brillouin scattering (SBS) was generated in the fiber and the phase of the reflection was compared to that of the pump using lateral shearing interferometers immediately after reflection and also after propagating back through the separate paths. To analyze the phase conjugating properties of SBS in the fiber, one of the paths included a pathlength oscillation. It was found that SBS from the long, graded-index fiber did not conjugate the phase of the pump. SBS formed a phase-locked beam immediately after reflection from the fiber, but did not lock the phases of the two beams after recombination as would be expected from a phase conjugate reflection.

Proceedings ArticleDOI
24 Feb 2008
TL;DR: Using a silicon waveguide based optical phase conjungator, mid-span dispersion compensation has been demonstrated by transmitting wavelength multiplexed 4×10 Gb/s data over 320 km standard fiber with <; 0.3 dB power penalty at bit error rate of 10-9.
Abstract: Using a silicon waveguide based optical phase conjungator, mid-span dispersion compensation has been demonstrated by transmitting wavelength multiplexed 4×10 Gb/s data over 320 km standard fiber with <; 0.3 dB power penalty at bit error rate of 10-9.

Journal ArticleDOI
TL;DR: In this article, the authors explored the occurrence of optical phase conjugation via stimulated Brillouin scattering (OPC-SBS) in weakly piezoelectric III-V semiconductor plasmas subjected to a large magnetostatic field under off-resonant transition regime.
Abstract: The occurrence of optical phase conjugation via stimulated Brillouin scattering (OPC-SBS) in weakly piezoelectric III–V semiconductor plasmas subjected to a large magnetostatic field under off-resonant transition regime has been explored theoretically. The reflectivity of the phase conjugate wave is dependent upon the Brillouin susceptibility and can be significantly enhanced through n-type doping of the crystal and the simultaneous application of a magnetostatic field. Moreover, the threshold pump intensity required for the occurrence of SBS in the crystal with finite optical attenuation can be considerably diminished through proper selection of the doping concentration and magnetostatic field. Consequently, OPC-SBS becomes a possible tool in phase-conjugate optics even under not-too-high power laser excitation by using doped n-type semiconductors kept under the influence of a large magnetostatic field. Numerical estimates made for n-InSb crystal at 77 K duly irradiated by a nanosecond pulsed 10.6 µm CO2...


01 Mar 2008
TL;DR: In this article, a numerical perturbation algorithm was constructed to search for the Stokes modal arrangement with the highest gain for a given pump input, assuming that all pump/Stokes modes decay/grow at the same rate, and that the fiber was lossless.
Abstract: : Stimulated Brillouin scattering in a multimode step-index fiber can be used to generate a counter-propagating, phase-conjugate beam that would prove useful in applications such as near diffraction limited, double-pass high-power amplifiers or coherent beam combination. Little modeling of such a fiber-based phase-conjugator has been done, making it difficult to make decisions about the right fiber to use. A numerical model was constructed with the aim of providing educated predictions about the phase conjugate fidelity that could be expected from a given pump intensity input coupled into a specific fiber. A numerical perturbation algorithm was constructed to search for the Stokes modal arrangement with the highest gain for a given pump input. The gain was calculated from the differential equation for the Stokes power assuming that all pump/Stokes modes decay/grow at the same rate, and that the fiber was lossless. The model proves to be much more accurate in predicting experimentally observed phase conjugate fidelities than previous efforts. In addition, the phenomenon of beam cleanup to higher order fiber modes is predicted and explained.

Proceedings ArticleDOI
15 Jun 2008
TL;DR: This architecture, for the first time, addresses virtually all of the shortcomings of the previously used mixer approaches to this problem and also exhibits other advantages such as excellent conversion gain, and the re-transmission of a low phase noise high power carrier.
Abstract: A new method for producing phase conjugation is presented. This is the essential component of a retrodirective array. This architecture, for the first time, addresses virtually all of the shortcomings of the previously used mixer approaches to this problem. The requirement for a frequency component at 2x F RF to be present is dispensed with. The architecture here does not require any frequency component higher than FRF, and also exhibits other advantages such as excellent conversion gain, and the re-transmission of a low phase noise high power carrier. Our solution involves the addition of a standard power combiner, used for vector summation, to a standard PLL. By using a novel four quadrant switching method, we can obtain reliable conjugation over a 360° phase range. Our circuit is ideally suited to low cost point to point self steered wireless applications such as video streaming.

Proceedings ArticleDOI
TL;DR: In this paper, an imaging scheme based on turbidity suppression optical phase conjugation (TSOPC) was proposed for depth selective targeting of planes within a turbid medium.
Abstract: We propose an imaging scheme based on turbidity suppression optical phase conjugation (TSOPC), allowing for depth selective targeting of planes within a turbid medium.

Patent
23 Jul 2008
TL;DR: In this paper, a non-linear refractivity test method based on phase conjugation and 4f phase coherent imaging technique was proposed to eliminate the effect of nonlinear absorption.
Abstract: The invention disclose an non-linear refractivity test method for eliminating the effect of non-linear absorption, which is based on phase conjugation and 4f phase coherent imaging technique, wherein a laser beam is filtered via a stop and focused on a sample via a Fourier lens, to be reflected to invert direction and pass the sample and the Fourier lens, the laser beam is splitted via a beam splitter to be attenuated and received by a CCD camera. The invention is characterized in that the invention respectively tests a non-sample picture, a linear picture, an absorption refractive picture and an absorption picture, respectively integrates the linear picture and non-sample picture to obtain the energy of the linear pulse after the sample and the total energy of the incident pulse, which ratio is the linear permeability of the sample, and the invention uses the absorption picture to digitally fit the absorption refractive picture to obtain the non-linear refractive index of the sample. The invention can obtain non-linear refractive index without the test on non-linear absorption factor, to eliminate the effect of non-linear absorption on test result and improve test accuracy.

Journal ArticleDOI
TL;DR: The introduction of an angular mismatch for the pump waves results, in the case of nonlocal photorefractive nonlinearity, in a strong almost twofold decrease of the threshold value of the coupling strength for the mirrorless optical oscillation.
Abstract: We show that the introduction of an angular mismatch for the pump waves results, in the case of nonlocal photorefractive nonlinearity, in a strong almost twofold decrease of the threshold value of the coupling strength for the mirrorless optical oscillation. This surprising feature will lead to a strong modification of the threshold and near-threshold behavior of a vast variety of optical oscillators based on the photorefractive phase conjugation and involving finite-size light beams.


Journal ArticleDOI
TL;DR: In this paper, a numerical model with layers of turbulence software was proposed by which point spread function (PSF), optical transfer function (OTF), as well as system isoplanatic angle can be calculated.
Abstract: The goal of this study was to analyse anisoplanatism of adaptive optics under an inhomogeneous turbulent atmosphere over a pupil of finite size. By means of a numerical model with layers of turbulence software was proposed by which point spread function (PSF), optical transfer function (OTF) as well as system isoplanatic angle can be calculated. Atmospheric turbulence was simulated with the aid of a set of moving random phase screens with arbitrary statistics. Both reference and target are assumed to be the point light sources. To simulate atmospheric turbulence we applied the concept of a number of moving random phase screens with Kolmogorov spectrum. In my investigation I used the model of the Shack-Hartmann wave front sensor and the ideal model of a wave front adaptive mirror that is assumed to reproduce a given number of Zernike polynomials without time delays. The designed software allows calculation of instantaneous and average values of phase correction errors at different angles between a reference beacon and target source. Simulations can be made with a broad range of parameters of an adaptive system and atmospheric turbulence. The system of the model allows changing of the control algorithm of phase correction. Both common phase conjugation and weighted phase conjugation algorithm have been tested. This program is capable of calculating the effects of beam diffraction during propagation in the atmosphere.