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Showing papers on "Phase conjugation published in 2011"


Journal ArticleDOI
TL;DR: Pairing two nonlinear metasurfaces formed by plasmonic nanoantennas loaded with χ(3) nonlinear elements put forward a realistic design for a time-reversal 'perfect lens', which can overcome the limitations in resolution and sensitivity to losses typical of negative-index lenses.
Abstract: We investigate the use of nonlinear metasurfaces formed by plasmonic nanoantennas loaded with χ(3) nonlinear elements, in order to realize subwavelength imaging based on phase conjugation and time reversal. The nanoantennas’ plasmonic resonance is used to boost the nonlinear response over an ultrathin surface, meeting the conditions for efficient phase conjugation necessary for imaging applications. Pairing two such surfaces, we put forward a realistic design for a time-reversal ‘perfect lens’, which can overcome the limitations in resolution and sensitivity to losses typical of negative-index lenses.

93 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined random sensor arrays from a compressive-sensing (CS) perspective, particularly in terms of the coherence of compressive sensing matrices, and demonstrated that the maximum sidelobe level of an array corresponds to the cosine coherence.
Abstract: Random sensor arrays are examined from a compressive-sensing (CS) perspective, particularly in terms of the coherence of compressive-sensing matrices. It is demonstrated that the maximum sidelobe level of an array corresponds to the coherence of interest for compressive sensing. This understanding is employed to explicitly quantify the accuracy of array source localization as a function of the number of sources and the noise level. The analysis demonstrates that the compressive-sensing theory is applicable to arrays in vacuum, as well as in the presence of a surrounding linear medium. Furthermore, the presence of a surrounding media with known properties may be used to improve array performance, with this related to phase conjugation and time reversal. Several numerical results are presented to demonstrate the theory.

62 citations


Journal ArticleDOI
TL;DR: A "black-box" phase sensitive amplifier is presented achieving simultaneous suppression of deterministic phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths.
Abstract: A "black-box" phase sensitive amplifier is presented achieving simultaneous suppression of deterministic phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths.

34 citations


Journal ArticleDOI
TL;DR: In the midinfrared where it is difficult to have high visibility of the fringes, it is demonstrated that local field corrections have a significant effect on the shape of the interference pattern.
Abstract: A detailed model is presented that describes the temporal and spectral interference patterns resulting from phase-recovery infrared–visible sum-frequency spectroscopy. Included in this model are the effects of dispersive elements other than the phase shifting unit placed between the sample and local oscillator signals. This inclusion is critical when considering the interference patterns arising from studies of buried interfaces. Furthermore, in the midinfrared where it is difficult to have high visibility of the fringes, it is demonstrated that local field corrections have a significant effect on the shape of the interference pattern. By collecting and subsequently fitting a two-dimensional interference pattern displaying both temporal and spectral fringes, a complete characterization of all these effects is possible.

30 citations


Journal ArticleDOI
TL;DR: In this paper, the first demonstration of 640-Gb/s return-to-zero ON-OFF keying channel transmission over a 100-km standard single-mode fiber link employing mid-pan phase conjugation is presented.
Abstract: We report the first demonstration of 640-Gb/s return-to-zero ON-OFF keying channel transmission over a 100-km standard single-mode fiber link employing midspan phase conjugation. A frequency-degenerate conjugate field spanning more than 20 nm is created in a low-birefringence parametric mixer for the first time. Physical separation of the conjugate field from the original field is enabled by utilizing pump polarization nondegeneracy. Rigorous link characterization using a high-quality 640-Gb/s transmitter and a high-sensitivity receiver revealed error-free (bit error ratio <;10-9) performance, eliminating the need for impractical fiber length control or electronic signal processing. The compatibility of wavelength-transparent conjugation with spectrally inefficient channel implies that channels with higher bit rates and better spectral efficiency can also be compensated.

29 citations


Proceedings ArticleDOI
06 Mar 2011
TL;DR: In this article, phase conjugation is proposed for nonlinearity compensation in fiber communications, where coherent detection and I/Q modulation are used to implement phase-conjugation.
Abstract: Electronic phase conjugation is proposed for nonlinearity compensation in fiber communications. Coherent detection and I/Q modulation are used to implement phase conjugation. Significant performance improvement is achieved in WDM multi-rate systems.

23 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that the ideal phase conjugating surface is in principle physically realizable and investigate the necessary properties of nonlinear and nonreciprocal particles which can be used to build a perfect lens system.
Abstract: It is theoretically known that a pair of phase conjugating surfaces can function as a perfect lens, focusing propagating waves and enhancing evanescent waves. However, the known experimental approaches based on thin sheets of nonlinear materials cannot fully realize the required phase conjugation boundary condition. In this paper we show that the ideal phase conjugating surface is in principle physically realizable and investigate the necessary properties of nonlinear and nonreciprocal particles which can be used to build a perfect lens system. The physical principle of the lens operation is discussed in detail and directions of possible experimental realizations are outlined.

20 citations


Journal ArticleDOI
TL;DR: This work solves the associated wave equations analytically, and gives an explicit formula for the reversal efficiency, and discusses the implementation for short optical electromagnetic pulses and shows that the new scheme may lead to their accurate time-reversal with efficiency higher than before.
Abstract: Recently, Chumak et al. have demonstrated experimentally the time-reversal of microwave spin pulses based on non-adiabatically tuning the wave speed in a spatially-periodic manner [Nat. Comm. 1, 141 (2010)]. Here, we solve the associated wave equations analytically, and give an explicit formula for the reversal efficiency. We discuss the implementation for short optical electromagnetic pulses and show that the new scheme may lead to their accurate time-reversal with efficiency higher than before.

18 citations


Patent
Xiang Zhou1, Guifang Li1, Eduardo F. Mateo1
10 Jan 2011
TL;DR: In this paper, an electronic phase conjugation system that receives an incoming optical signal from a first section of a fiber optic link, converts the incoming optical signals to an in-phase electric signal and a quadrature electrical signal, and generates a phase-conjugated outgoing optical signal, compensating for impairment of the fiber in the communication system.
Abstract: Exemplary embodiments include a method and systems for impairment compensation in a communication system. The systems can include an electronic phase conjugation system that receives an incoming optical signal from a first section of a fiber optic link, converts the incoming optical signal to an in-phase electric signal and a quadrature electrical signal, and generates a phase conjugated outgoing optical signal from the in-phase and quadrature electrical signals. The phase conjugated outgoing optical signal compensates for impairment of the fiber in the communication system.

14 citations


Patent
03 Mar 2011
TL;DR: An optical phase conjugator that can be deployed within a long-haul fiber-optic link of an optical WDM system to improve the system's tolerance to intra-and inter-channel nonlinear effects is presented in this paper.
Abstract: An optical phase conjugator that can be deployed within a long-haul fiber-optic link of an optical WDM system to improve the system's tolerance to intra- and inter-channel nonlinear effects. In one embodiment, the optical phase conjugator has a digital signal processor configured to perform, in the digital electrical domain, a phase-conjugation transformation for various components of a WDM signal so that certain signal distortions imposed on that signal in the front portion of the fiber-optic link are reduced in the back portion of the link. Advantageously, the optical phase conjugator is flexibly configurable to employ an input-to-output carrier-frequency-mapping configuration that is most beneficial under particular operating conditions. mapping configuration that is most beneficial under particular operating conditions.

14 citations


Journal ArticleDOI
TL;DR: Detailed characterization of EBS can be used for metrology of scattering materials and a three dimensional intensity peak is predicted in free space at a point conjugate to the source and is experimentally observed.
Abstract: Enhanced backscattering (EBS), also known as weak localization of light, is derived using the Huygens–Fresnel principle and backscattering is generally shown to be the sum of an incoherent baseline and a phase conjugated portion of the incident wave that forms EBS. The phase conjugated portion is truncated by an effective aperture described by the probability function P(s) of coherent path-pair separations. P(s) is determined by the scattering properties of the medium and so characterization of EBS can be used for metrology of scattering materials. A three dimensional intensity peak is predicted in free space at a point conjugate to the source and is experimentally observed.

Journal ArticleDOI
TL;DR: In this paper, a nondegenerate phase-conjugate wave was generated via stored atomic coherence in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal based on the electromagnetically induced transparency effect, and its capability for wavefront reconstruction of phase distortion was demonstrated experimentally.
Abstract: A nondegenerate phase-conjugate wave was generated via stored atomic coherence in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal based on the electromagnetically induced transparency effect, and its capability for wave-front reconstruction of phase distortion was demonstrated experimentally. The phase-matching condition during the storage-retrieval process of the phase-conjugate wave was characterized both experimentally and theoretically in detail. Theoretical simulations fit the experimental data very well. Such a scheme of storage and retrieval of the phase-conjugate wave may have potential applications in optical signal processing and information security.

Journal ArticleDOI
TL;DR: In this article, the authors proposed an optimized optical phase conjugation (OPC) configuration for the 40-Gb/s CO-OFDM system, which can further improve system performances and increase nonlinear compensation effectiveness.
Abstract: The optimized optical phase conjugation (OPC) configuration is proposed for the 40-Gb/s CO-OFDM system. The proposed configuration for nonlinear cancellation is systematically depicted in transmission links with lumped amplification. Numerical simulations are performed to demonstrate effectiveness. Simulation results show that mid-span spectral inversion (MSSI) can partially compensate for nonlinear distortions. Moreover, its optimized configuration can further improve system performances and increase nonlinear compensation effectiveness. Compared with MSSI, the maximal Q factor, nonlinear threshold, and transmission distance of optimized OPC configuration increase by over 1.6 dB, 2 dB, and 2 times, respectively.

Proceedings ArticleDOI
01 May 2011
TL;DR: In this article, the authors used ultrafast Fourier-plane OPA imaging to image, wavelength shift, and amplify complex two-dimensional objects with spatial features from 1.1 to 11.3 line-pairs/mm, corresponding to a 2D spacebandwidth product (SBP) of 13,790.
Abstract: We used ultrafast Fourier-plane OPA imaging to image, wavelength-shift, and amplify complex two-dimensional objects with spatial features from 1.1 to 11.3 line-pairs/mm, corresponding to a 2D space-bandwidth product (SBP) of 13,790.

Proceedings ArticleDOI
TL;DR: In this paper, a novel adaptive optical closed loop system with water-cooled bimorph mirror as a wavefront stabilizer was proposed to compensate for the aberrations of high-power CW laser beam.
Abstract: This paper discusses the novel adaptive optical closed loop system with water-cooled bimorph mirror as a wavefront corrector to compensate for the aberrations of high-power CW laser beam. Shack-Hartmann wavefront sensor is used as an element for feedback control. Comparison of phase conjugation and modified hill-climbing technique is shown.

Proceedings ArticleDOI
18 Sep 2011
TL;DR: In this paper, the authors demonstrate a black-box phase sensitive amplifier able to provide simultaneous suppression of phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths.
Abstract: For the first time we demonstrate a “black-box” phase sensitive amplifier able to provide simultaneous suppression of phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths.

Journal ArticleDOI
TL;DR: Results of tests on a VBG designed to resolve wavelengths 0.060 nm apart are reported, corresponding to the 16 GHz frequency shift for SBS backscattering at 1064 nm in fused silica.
Abstract: A master-oscillator power-amplifier with stimulated Brillouin scattering (SBS) beam cleanup or wavefront reversal typically incorporates a Faraday isolator to outcouple the Stokes light, limiting the power scalability. Volume Bragg gratings (VBGs) have the potential for scaling to higher powers. We report here the results of tests on a VBG designed to resolve wavelengths 0.060 nm apart, corresponding to the 16 GHz frequency shift for SBS backscattering at 1064 nm in fused silica. Such an element may also find use in between stages of fiber amplifiers, for blocking the Stokes wave.

Journal ArticleDOI
TL;DR: In this article, an experimentally stimulated Brilluoin scattering (SBS) of vortex laser beams, namely, the LG11 and LG01 Laguerre -Gaussian modes, was shown to become phase conjugate by destroying the laser mode structure in the SBS cell.
Abstract: We study experimentally stimulated Brilluoin scattering (SBS) of vortex laser beams, namely, the LG11 and LG01 Laguerre -Gaussian modes. The wave front transformation is experimentally demonstrated in the case of SBS of the LG11 laser mode, directly focused into the SBS cell, when the fundamental Gaussian mode LG00 rather than the conjugate mode is selected from the Stokes beam. It is shown that optical vortices become phase conjugate by destroying the laser mode structure in the SBS cell. Phase conjugation (PC) of the LG01 and LG11 modes is obtained in the SBS mirror using a regular aberrator (microlens raster) in the system of laser beam focusing into the SBS cell.

Journal ArticleDOI
TL;DR: In this paper, a theoretical study of optical phase conjugation by degenerate four-wave mixing in one-dimensional photonic crystals containing two kinds of single-negative materials is presented.
Abstract: We present a theoretical study of optical phase conjugation by degenerate four-wave mixing in one-dimensional photonic crystals containing two kinds of single-negative materials. Compared to usual photonic crystals with the same thickness and third-order nonlinear susceptibility (χ3), the generation efficiency of the optical phase-conjugate wave can be enhanced by nearly 3 orders of magnitude. Distinct from the band-edge state in usual photonic crystals, the enhancement is caused by the strong field localized at each interface of two types of single-negative materials. Owing to the unique properties of the band edge of the zero-effective-phase gap that is insensitive to the angle of incidence, the optical phase-conjugate wave can be generated efficiently in a wide range of angle of incidence.

Journal ArticleDOI
TL;DR: The phase conjugation regime is experimentally implemented in a cell with a liquid (water, ethanol, carbon tetrachloride) at the four-wave mixing of counter-propagating beams of diode lasers as discussed by the authors.
Abstract: The phase conjugation regime is experimentally implemented in a cell with a liquid (water, ethanol, carbon tetrachloride) at the four-wave mixing of counter-propagating beams of diode lasers. Intracavity enhancement of the conjugate wave and the wave of the coherent anti-Stokes Raman scattering (CARS) arising in the interaction of the conjugate wave and one of the pumping waves in CARS scheme is detected. The latter process occurs in a narrow spectral range when the geometry of the wave vectors of the interacting waves in CARS scheme ensures arrival of the CARS signal at the laser aperture. It is found out that the quality of the four-photon phase conjugate mirror in the given interaction scheme is very sensitive to any perturbations (mechanical, acoustic, thermal, etc.) of the induced grating in the sample, which manifests itself in the distortion of the signal spectrum.


Posted Content
TL;DR: In this article, the use of phase conjugation in one arm of a correlated two-photon imaging apparatus allows undistorted ghost imaging through a region with randomly-varying phase shifts.
Abstract: It is shown that the use of phase conjugation in one arm of a correlated two-photon imaging apparatus allows undistorted ghost imaging through a region with randomly-varying phase shifts. The images are formed from correlated pairs of photons in such a way that turbulence-induced phase shifts gained by the photons during passage through the medium cancel pairwise.

Proceedings ArticleDOI
TL;DR: Barium titanate (BaTiO 3 ) is a good candidate for phase conjugation on the nano-scale, as four-wave mixing has been shown in nanoparticles of this type.
Abstract: Barium titanate (BaTiO 3 ) is a good candidate for phase conjugation on the nano-scale, as four-wave mixing has been shown in nanoparticles of this type. Also, the ability to dope this material with rare earth elements, with strong absorption and emission lines, makes it possible to use these as multi-functional, multi-modal probes for biomedical applications. BaTiO 3 nanoparticles are synthesized using a precipitation method and fully characterized. These particles are used in a four wave mixing setup to optically conjugate scattered light traveling through turbid media, such as tissue, to re-obtain lost image information due to the scattering process.

Proceedings ArticleDOI
22 May 2011
TL;DR: In this paper, the dispersion properties of planar planar photonic crystal waveguides have been investigated for four-wave mixing in short (80 µm) dispersion engineered slow light silicon photonic crystals.
Abstract: Recently, planar photonic crystals (PhCs) have emerged as one possible and flexible platform for integrating various optical components onto the same chip. Of the extraordinary dispersion properties that are exhibited by planar PhC waveguides lies the possibility of significantly reducing the group velocity at which light propagates [1]. Most significantly, combining slow light PhCs with a nonlinear medium enhances all kinds of optical nonlinear processes [2], with the potential for realising compact all-optical nonlinear devices that operate at low power. In addition to providing slow light propagation, PhC waveguides can be further engineered, so that slow light modes can present very low dispersion. A number of approaches have been used to achieve this, for example by slightly modifying the geometry of the PhC waveguide [3] or by using selective liquid infiltration [4]. The possibility of managing the dispersion in PhC waveguides is highly advantageous, as it provides a way to control higher order dispersion parameters in addition to the group velocity for optimizing processes that strongly depend on dispersive characteristics and nonlinearities. In our previous works, we have investigated both numerically [5] and experimentally [6] four-wave mixing (FWM) in short (80 µm) dispersion engineered slow light silicon photonic crystal waveguides. Compared with silicon PhC waveguides, chalcogenide waveguides do not suffer from two photon absorption (TPA) and free carrier absorption (FCA). Therefore, the high nonlinearity of chalcogenide glass and merging it with slow light in photonic crystals can potentially be used to make a very compact GVD and SPM compensation device. Mid-span phase conjugation is a technique that can compensate for both GVD and SPM, thereby allowing higher power transmission with fewer amplifiers.

Proceedings ArticleDOI
22 May 2011
TL;DR: A novel processing method is proposed to select time delayed arrivals from the received probe, and this method can also suppress the noise level for the truncated probe signal.
Abstract: Underwater acoustic communication by passive-phase conjugation uses a channel probe signal transmitted prior to the data signal in order to estimate the channel response. At the receiver, the received probe signal can be truncated to correlate with the late arrived data signal. In a multipath channel, there are paths that undergo incoherent scattering by the sea surface, and they decrease the coherence between the estimated channel response and the channel response for data signal. For a linear frequency modulation probe signal, a novel processing method is proposed to select time delayed arrivals from the received probe, and this method can also suppress the noise level for the truncated probe signal. Applying this method to the data collected in a sea trial, the communication performance is improved.

Proceedings ArticleDOI
24 Oct 2011
TL;DR: In this article, phase conjugation was used for compensating dispersion in an optical transmission system with 10 Gb/s as bit rate and for a distance of over 50,000 kms.
Abstract: Chromatic Dispersion is one of the major (Linear) effect in Optic transmission System. Dispersion causes broadening of transmitted pulses that leads to Inter Symbol Interference (ISI). In this paper, analysis of phase conjugation in compensating dispersion in an optical transmission system with 10 Gb/s as bit rate and for a distance of over 50,000 kms. The required number and fashion of OPC to be used for effective dispersion compensation were analysed in DWDM systems. Simulation results were obtained using OPTSIM software from Rsoft.

Journal ArticleDOI
TL;DR: In this paper, photorefractive Sb-doped Sn2P2S6 samples of different crystal thickness were used to investigate the properties of the media for double phase conjugation.
Abstract: We developed photorefractive Sb-doped Sn2P2S6 samples of different crystal thickness to investigate the properties of the media for double phase conjugation. The Sn2P2S6:Sb crystals have high coupling coefficient of 20 cm−1, and show fast response time of 1.3 ms at total incident intensity of 0.3 W/cm2. The maximum phase conjugate reflectivity of 32% was observed with a 4 mm thickness sample. To investigate the characteristics of Sn2P2S6:Sb for double phase conjugation, on the basis of the coupled wave equations, we showed the dependence of phase conjugate reflectivity on incident angle, crystal thickness, total incident intensity and polarization. From these results, the optimum incident condition was clarified for obtaining the highest phase conjugate reflectivity.


Journal ArticleDOI
TL;DR: It is found that the distortion in the hologram could be compensated while avoiding interpage crosstalk and that the bit error rates of the reproduced data could be decreased and the optimized wavefront could compensate for distortions in several neighboring data pages.
Abstract: We are studying a form of holographic data storage with phase conjugation, and we compensated for hologram distortion due to shrinkage of photopolymer materials in the holographic medium by controlling the wavefront of the reference beam. When a high NA lens and narrow angle interval of angle multiplexing are employed to obtain a high data recording density, some wavefronts cause interpage crosstalk on the reconstructed image. We tried to determine the moving range of actuators in a deformable mirror for controlling the wavefront. As a result, we found that the distortion in the hologram could be compensated while avoiding interpage crosstalk and that the bit error rates of the reproduced data could be decreased. We also found that the optimized wavefront could compensate for distortions in several neighboring data pages. This method can ensure a high data recording density in holographic data storage.

Proceedings ArticleDOI
TL;DR: In this paper, the authors proposed a new time-reversal scheme for optical pulses which overcomes the limitations of exisitng schems and demonstrated highly efficient and broadband reversal of pulses of 100 fs and 10 ps duration.
Abstract: We propose a new time-reversal scheme for optical pulses which overcomes the limitations of exisitng schems. We demonstrate highly efficient and broadband reversal of pulses of 100 fs and 10 ps duration.