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Showing papers on "Phase conjugation published in 2010"


Journal ArticleDOI
TL;DR: A novel high capacity (number of degrees of freedom) open loop adaptive optics method, termed DOPC, which provides a robust optoelectronic optical phase conjugation (OPC) solution and is employed to show that the reversing of random scattering in turbid media by phase conjugal force is surprisingly robust and accommodating of phase errors.
Abstract: In this work, we report a novel high capacity (number of degrees of freedom) open loop adaptive optics method, termed digital optical phase conjugation (DOPC), which provides a robust optoelectronic optical phase conjugation (OPC) solution. We showed that our prototype can phase conjugate light fields with ~3.9 x 10−3 degree accuracy over a range of ~3 degrees and can phase conjugate an input field through a relatively thick turbid medium (μsl ~13). Furthermore, we employed this system to show that the reversing of random scattering in turbid media by phase conjugation is surprisingly robust and accommodating of phase errors. An OPC wavefront with significant spatial phase errors (error uniformly distributed from – π/2 to π/2) can nevertheless allow OPC reconstruction through a scattering medium with ~40% of the efficiency achieved with phase error free OPC.

337 citations


Journal ArticleDOI
TL;DR: It is shown that the phase-conjugated focus can be displaced from its initial position by illuminating the same region of the turbid layer with an angular offset by using digital phase conjugation of the second harmonic field radiated from a beacon nanoparticle.
Abstract: We demonstrate imaging through a turbid layer by using digital phase conjugation of the second harmonic field radiated from a beacon nanoparticle. We show that the phase-conjugated focus can be displaced from its initial position by illuminating the same region of the turbid layer with an angular offset. An image is obtained by scanning the phase-conjugated focus through the turbid layer in a region around the nanoparticle. We obtain a clear image of the target by measuring the light transmitted through it when scanning the focused beam.

225 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate polarizer-free and fast response microlens arrays based on optical phase modulation of polymer-stabilized blue phase liquid crystal (PSBP-LC).
Abstract: We demonstrate polarizer-free and fast response microlens arrays based on optical phase modulation of polymer-stabilized blue phase liquid crystal (PSBP-LC). Polarization-independent optical phase shift is because the propagation of an incident light is along the optic axis of PSBP-LC, and birefringence of PSBP-LC induced by Kerr effect results in electrically tunable optical phase shift. The measured optical phase shift of a PSBP-LC phase modulation is around π radian at 150 Vrms for the cell gap of 7 μ. The response time is about 3 ms. The focal length is around 13.1 cm at 100 Vrms.

219 citations


Journal ArticleDOI
TL;DR: This work demonstrates focusing coherent light on a nanoparticle through turbid media based on digital optical phase conjugation of second harmonic generation (SHG) field from the nanoparticle.
Abstract: We demonstrate focusing coherent light on a nanoparticle through turbid media based on digital optical phase conjugation of second harmonic generation (SHG) field from the nanoparticle. A SHG active nanoparticle inside a turbid medium was excited at the fundamental frequency and emitted SHG field as a point source. The SHG emission was scattered by the turbid medium, and the scattered field was recorded by off-axis digital holography. A phase-conjugated beam was then generated by using a phase-only spatial light modulator and sent back through the turbid medium, which formed a nearly ideal focus on the nanoparticle.

187 citations


Journal ArticleDOI
TL;DR: In this article, the theory of monochromatic time-reversal mirrors (TRM) or equivalently phase conjugate mirrors is developed for electromagnetic waves, and a differential expression similar to the Lorentz reciprocity theorem is deduced.
Abstract: The theory of monochromatic time-reversal mirrors (TRM) or equivalently phase conjugate mirrors is developed for electromagnetic waves. We start from the fundamental time-symmetry of the Maxwell's equations. From this symmetry, a differential expression similar to the Lorentz reciprocity theorem is deduced. The radiating conditions on TRM are expressed in terms of 6-dimension Green's functions. To predict the time reversal focusing on antenna arrays, a formalism that involves impedance matrix is developed. We show that antenna coupling can dramatically modify the focal spot. Especially, we observe, that in some circumstances, sub-wavelength focusing on a bi-dimensional array may arise.

126 citations


Journal ArticleDOI
TL;DR: The experimental findings address the minimum speed limit of a broad range of optical time reversal experiments for in vivo applications on tissues with a consistent decay time of less than two seconds.
Abstract: We present a holography-based in vivo optical phase conjugation experiment performed on a living rabbit ear. The motion of live tissues caused the phase conjugate signal to decay with a consistent decay time of less than two seconds. We monitor the signal decay time variation after the ear is excised to postulate different mechanisms that cause the signal decay. The experimental findings address the minimum speed limit of a broad range of optical time reversal experiments for in vivo applications on tissues.

103 citations


Journal ArticleDOI
TL;DR: An experimental demonstration of phase conjugation using nonlinear metamaterial elements using active split-ring resonators loaded with varactor diodes to produce a time-reversed signal.
Abstract: We present an experimental demonstration of phase conjugation using nonlinear metamaterial elements. Active split-ring resonators loaded with varactor diodes are demonstrated theoretically to act as phase-conjugating or time-reversing discrete elements when parametrically pumped and illuminated with appropriate frequencies. The metamaterial elements were fabricated and shown experimentally to produce a time-reversed signal. Measurements confirm that a discrete array of phase-conjugating elements act as a negatively refracting time-reversal rf lens only $0.12\ensuremath{\lambda}$ thick.

80 citations


Journal ArticleDOI
TL;DR: In this article, the amplitude and resolution trends of the sig- nals acquired by turbidity suppression through optical phase conjuga- tion TSOPC with samples that span the ballistic and diffusive scat- tering regimes were described.
Abstract: We describe the amplitude and resolution trends of the sig- nals acquired by turbidity suppression through optical phase conjuga- tion TSOPC with samples that span the ballistic and diffusive scat- tering regimes. In these experiments, the light field scattered through a turbid material is written into a hologram, and a time-reversed copy of the light field is played back through the sample. In this manner, the wavefront originally incident on the sample is reconstructed. We ex- amine a range of scattering samples including chicken breast tissue sections of increasing thickness and polyacrylamide tissue-mimicking phantoms with increasing scattering coefficients. Our results indicate that only a small portion of the scattered wavefront 0.02% must be collected to reconstruct a TSOPC signal. Provided the sample is highly scattering, all essential angular information is contained within such small portions of the scattered wavefront due to randomization by scattering. A model is fitted to our results, describing the depen- dence of the TSOPC signal on other measurable values within the system and shedding light on the efficiency of the phase conjugation process. Our results describe the highest level of scattering that has been phase conjugated in biological tissues to date. © 2010 Society of

45 citations


Journal ArticleDOI
TL;DR: In this paper, the authors considered optical phase conjugation (OPC) as an approach to suppress well-matched FWM processes and derived an analytical formula accurately predicting the degree of suppression.
Abstract: Coherent optical orthogonal frequency-division multiplexed (OFDM) systems must be carefully designed to minimize the detrimental impact of fiber nonlinearity manifested through four-wave mixing (FWM). Because of the small subcarrier spacing associated with OFDM, a significant fraction of FWM processes is well matched, resulting in a rapid buildup of FWM light with propagation distance. In this paper, we consider optical phase conjugation (OPC) as an approach to suppress such well-matched FWM processes. An analytical formula accurately predicting the degree of suppression is derived and discussed. It is shown that when combined with the methods previously proposed in the literature, the application of OPC can dramatically reduce the overall FWM power accumulated within the link for a wide range of crucial design parameters.

42 citations


Journal ArticleDOI
TL;DR: In this article, the imaging properties of a phase conjugating lens operating in the far field zone of the imaged source and augmented with scatterers positioned in the source near field region are theoretically studied.
Abstract: The imaging properties of a phase conjugating lens operating in the far field zone of the imaged source and augmented with scatterers positioned in the source near field region are theoretically studied in this paper. The phase conjugating lens consists of a double sided 2D assembly of straight wire elements, individually interconnected through phase conjugation operators. The scattering elements are straight wire segments which are loaded with lumped impedance loads at their centers. We analytically and numerically analyze all stages of the imaging process; i) evanescent-to-propagating spectrum conversion; ii) focusing properties of infinite or finite sized phase conjugating lens; iii) source reconstruction upon propagating-to-evanescent spectrum conversion. We show that the resolution that can be achieved depends critically on the separation distance between the imaged source and scattering arrangement, as well as on the topology of the scatterers used. Imaged focal widths of up to one-seventh wavelength are demonstrated. The results obtained indicate the possibility of such an arrangement as a potential practical means for realising using conventional materials devices for fine feature extraction by electromagnetic lensing at distances remotely located from the source objects under investigation.

37 citations


Journal ArticleDOI
TL;DR: The concepts, advantages, and disadvantages of phase conjugation techniques are introduced, and the self-phasing characteristic and technical difficulties of the array are presented.
Abstract: This paper presents an overview on the phase conjugation techniques of the retrodirective antenna array. The concepts, advantages, and disadvantages of phase conjugation techniques are introduced. The self-phasing characteristic and technical difficulties of the array are presented as well as their structures and applications. Further researches in this area are presented finally.

Journal ArticleDOI
TL;DR: A new RADAR system able to perform Phase Conjugation experiments over the ultrawideband (2{4)GHz) and the excellent agreement between measured and theoretical results validates the potential of the system.
Abstract: We present a new RADAR system able to perform Phase Conjugation experiments over the ultrawideband (2{4)GHz. The system is equipped with a transmit/receive linear array made of eight antennas connected to a 2-port Vector Network Analyzer through eight independent couples of digitally-controlled RF attenuators and phase shifters. Thus, each channel can selectively transmit or receive and can as well attenuate and phase shift the RF signal. For each frequency, either the Phase Conjugation or the Decomposition of the Time Reversal Operator (DORT) is applied to the received signal and the appropriate amplitude and phase law is coded into the prototype; the focusing wave is then experimentally re-emitted by the array. The quality of the achieved backpropagation is evaluated both in frequency and time domain: In this sense we can speak of Time Reversal. The excellent agreement between measured and theoretical results validates the potential of our system.

Journal ArticleDOI
TL;DR: Experimental demonstration of an all-optical continuously tunable delay line based on parametric mixing with a total delay range of 7.34 mus, capable of minimizing the residual dispersion for the entire tuning range is reported.
Abstract: We report experimental demonstration of an all-optical continuously tunable delay line based on parametric mixing with a total delay range of 7.34 μs. The bit-error rate performance of the delay line was characterized for a 10-Gb/s NRZ data channel. This result is enabled by cascading a discrete delay line that consists of 16 wavelength-dependent delays and a continuously tunable delay stage. Four wavelength conversion stages based on four-wave mixing in silicon waveguides were performed in order to achieve wavelength-preserving operation. The wavelength-optimized optical phase conjugation scheme employed in the delay line is capable of minimizing the residual dispersion for the entire tuning range.

Journal ArticleDOI
TL;DR: The first demonstration of optical phase conjugation (OPC) transmission of phase encoded and wavelength-division multiplexed (WDM) signals by the Kerr effect in a planar structured waveguide is reported.
Abstract: This work was supported by the Australian Research Council (ARC) through its ARC Centres of Excellence and Federation Fellowship programs.

Journal ArticleDOI
TL;DR: In this paper, the Bose-Hubbard model was used to reverse the dynamics of cold bosonic atoms in an optical lattice in the regime described by the BH model.
Abstract: Time reversal is an oft-used technique to probe and measure a quantum system. In particular, it is key for some theoretical information approaches to quantum criticality like fidelity decay. Here proposed is how to reverse the dynamics of cold bosonic atoms in an optical lattice in the regime described by the Bose-Hubbard model. The proposed experiment uses proven techniques—a linear phase imprint on the lattice, and a change in magnetic field to tune the boson-boson scattering length through a Feshbach resonance. The sensitivity of quantum dynamics across the insulator-superfluid quantum phase transition of the Bose-Hubbard model is studied, and sensing applications of dynamic reversals such as measuring the intensity of external potentials (e.g., gravity) is discussed.

Journal ArticleDOI
TL;DR: It is demonstrated that it is possible to obtain significant nonlinearity compensation, but that no improvement is obtained using configurations specifically aimed at the compensation of the nonlinear phase noise.
Abstract: We experimentally compare the effectiveness of three different optical-phase-conjugation-based nonlinearity-compensation strategies on a transmission system employing phase-modulated signals, and hence affected by the Gordon-Mollenauer effect. We demonstrate that it is possible to obtain significant nonlinearity compensation, but that no improvement is obtained using configurations specifically aimed at the compensation of the nonlinear phase noise.

Journal ArticleDOI
TL;DR: It is shown that not only single counter-propagating traps can be implemented by phase-conjugation, but also structured light fields can be used and can be rearranged in real-time and allow for interactive dynamic manipulation.
Abstract: Counter-propagating optical traps are widely used where long working distances, axially symmetric trapping potentials, or standing light waves are required. We demonstrate that optical phase-conjugation can automatically provide a counter-propagating replica of a wide range of incident light fields in an optical trapping configuration. The resulting counter-propagating traps are self-adjusting and adapt dynamically to changes of the input light field. It is shown that not only single counter-propagating traps can be implemented by phase-conjugation, but also structured light fields can be used. This step towards more complex traps enables advanced state-of-the-art applications where multiple traps or other elaborated trapping scenarios are required. The resulting traps cannot only be used statically, but they can be rearranged in real-time and allow for interactive dynamic manipulation.

Journal ArticleDOI
TL;DR: In this article, the phase conjugated energy and inductive loading of the constituent lens wire elements is shown to be essential for sub-wavelength focusing since this leads to the creation of a phase-conjugated near field predominantly determined by a convolution of the array current distribution with the real part of the Greens function which oscillates at a subwavelength scale.
Abstract: The properties of a lumped loaded wire array as a means for near field focusing using phase conjugation is studied. The constructive role of phase conjugation in the near field image formation is justified both analytically and numerically. The generation of phase conjugated energy and how this is influenced by lumped impedance loading of the wires constituting the lens is discussed. In particular it is shown that inductive loading of the constituent lens wire elements is essential for subwavelength focusing since this leads to the creation of a phase conjugated near field predominantly determined by a convolution of the array current distribution with the real part of the Greens function which oscillates at a subwavelength scale. The characteristic resolution of the lens in terms of the full width at half maximum is shown to be ~ λ/7 for a single source and better than λ/4 for two dipole sources at λ/10 source-lens separation distance.

Proceedings ArticleDOI
TL;DR: In this article, the authors propose a mode division multiplex communication technique that can split a specific spatial mode in light from a spatial mode multiplexed in an optical fiber by fusion of a phase conjugation technique with spatial filtering processing by multiple-ed volume holograms and random diffusers.
Abstract: We propose mode division multiplex communication technique that can split a specific spatial mode in light from a spatial mode multiplexed in an optical fiber by fusion of a phase conjugation technique with spatial filtering processing by multiplexed volume holograms and random diffusers. In mode division multiplexing, the optical signal outgoing from the multimode optical fiber is in a condition that optical inform ation of plural spatial modes is overlapped, therefore it is difficult to de-multiplex electrically after light detection. Our technique enables to split it into each mode all optically and to compensate temporal modal shift dynamically. Mode de-multiplexing is realized by multiplexed holographic arithmetic device and phase matching of a wave surface for the spatial mode orthogonal to time. Therefore, if we use indices in conventional electronic processing, a very high-speed operation equivalent to that of 10-100PFLOPS can be realized without causing any delay in light information to be transmitted. Moreover, it can realize constructions of a system that can dynamically respond to temporal mode variations and distortions with fiber transmissions by using a photorefractive medium. Separating of around 60-70% was ach ieved in an experiment of separating three multiplexed spatial modes by controlling a volume type dynamic reconfigurable device based on LiNbO

Journal ArticleDOI
TL;DR: In this paper, the authors experimentally demonstrate collisions between two copropagating parallel coherent beams inside the photorefractive semiconductor iron doped indium phosphide (InP:Fe) at λ = 1064
Abstract: In this paper, we experimentally demonstrate collisions between two copropagating parallel coherent beams inside the photorefractive semiconductor iron doped indium phosphide (InP:Fe) at λ=1064 nm.

Journal ArticleDOI
TL;DR: Reflectionless transmission of light waves with unitary transmittance is shown to occur in a certain class of gain-grating structures and phase-conjugation mirrors in the unstable regime of supersymmetric relativistic quantum mechanics.
Abstract: Reflectionless transmission of light waves with unitary transmittance is shown to occur in a certain class of gain-grating structures and phase-conjugation mirrors in the unstable (above-threshold) regime. Such structures are synthesized by means of the Darboux method developed in the context of supersymmetric relativistic quantum mechanics. Transparency is associated to superluminal pulse transmission.

Journal ArticleDOI
TL;DR: In this paper, a robust method for obtaining the helical interference pattern due to the phase-conjugation of an isolated optical vortex by means of the non-holographic technique is proposed.
Abstract: The robust method for obtaining the helical interference pattern due to the phase-conjugation of an isolated optical vortex by means of the non-holographic technique is proposed It is shown that a perfect wavefront reversal of the vortex in a linear polarization state via an even number of reflections is achievable due to the turn of the photon’s momentum p≈ℏk with respect to the photon’s orbital angular momentum projection Lz The possible experimental realization is based on cat’s eye-prism-like reflections inside the confocal optical loop cavity The alternative scheme contains the Dove prism embedded in the optical loop with an odd number of reflections from mirrors This confocal interferometric technique is applicable to optical tweezers, atomic traps, Sagnac laser loops, and metamaterials fabrication

Journal ArticleDOI
TL;DR: In this Letter, a first (to the authors' knowledge) demonstration of phase conjugate self-organized coherent beam combination is reported, involving combination of two self-adaptive gain grating holographic laser resonators.
Abstract: In this Letter, a first (to our knowledge) demonstration of phase conjugate self-organized coherent beam combination is reported. A demonstration involving combination of two self-adaptive gain grating holographic laser resonators is presented. Output powers of up to 27 W, with a combination efficiency of 94%, are demonstrated. This technique coherently combines individual phase conjugate laser modules, which do not have predefined spectral or spatial modes. This removes the problem of finding shared resonator modes, which should allow coherent beam combination of much larger laser arrays than standard self-organized coherent beam combination.

Journal ArticleDOI
TL;DR: For the first time to the authors' knowledge, on picosecondpulse optical phase conjugation using photorefractive Sn(2)P( 2)S(6) crystals, phase-conjugate reflectivities of up to 45% with very fast build-up times are achieved.
Abstract: We report, for the first time to our knowledge, on picosecond-pulse optical phase conjugation using photorefractive Sn2P2S6 crystals. For 7.2-ps pulses at 1.06 μm, we have achieved phase-conjugate reflectivities of up to 45% with very fast build-up times, about 15 ms at an intensity of 23 W/cm2 using Te-doped Sn2P2S6. We furthermore demonstrate aberration-free 5 W optical output of 8-ps pulses at 1.06 μm from a side pumped Nd:YVO4 amplifier using the Sn2P2S6-based phase-conjugate feedback.

Journal ArticleDOI
TL;DR: This work demonstrates 160 Gbit/s return-to-zero (RZ) differential quarternary phase-shift keying (DQPSK) signal transmission over a 110 km single-mode fiber by taking advantage of mid-span optical phase conjugation (OPC) and shows the polarization insensitivity of the OPC system using a polarization diversity scheme.
Abstract: We demonstrate 160Gbit/s return-to-zero (RZ) differential quarternary phase-shift keying (DQPSK) signal transmission over a 110km single-mode fiber by taking advantage of mid-span optical phase conjugation (OPC). The technique is based on nonlinear wavelength conversion by cascaded second harmonic and difference frequency generation in a Ti:PPLN waveguide. Error-free operation with a negligible optical signal-to-noise ratio penalty for the signal after the OPC transmission without and with polarization scrambling was achieved. The results also show the polarization insensitivity of the OPC system using a polarization diversity scheme.

Journal ArticleDOI
TL;DR: In this paper, a phase conjugation of evanescent waves is considered in the case of propagating waves and four wave mixing in BaTiO3 is shown to provide efficient backward and forward phase conjogation over a major part of the angular spectrum, taking advantage of internal reflections inside the non-linear slab.
Abstract: A new route toward a lossless superlens has been proposed recently. It relies on the association of two phase-conjugating sheets. The aim of this study is to show how such a lens can be implemented experimentally at optical frequencies. Because efficient phase conjugation of evanescent waves is illusory with the current technology, only the case of propagating waves is considered here. Four wave mixing in BaTiO3 is shown to provide efficient backward and forward phase conjugation over a major part of the angular spectrum, taking advantage of internal reflections inside the non-linear slab. However, phase distortions arise for high spatial frequencies and limit the resolving power of the device. The addition of a second phase-conjugator automatically compensates for these phase distortions. The wave field is then perfectly translated through the system. Actually, such a device performs even better than a negative refracting lens since the association of two phase-conjugating mirrors behaves like a resonant cavity. An amplification of the wave field by a factor of 102 in intensity is predicted, despite the important absorption in BaTiO3.

Proceedings ArticleDOI
21 Jun 2010
TL;DR: In this article, a novel technique to realize true time reversal of an optical signal, using dynamic Brillouin gratings in high-birefringence fibers, is proposed.
Abstract: A novel technique to realize true time reversal of an optical signal, using dynamic Brillouin gratings in high-birefringence fibers, is proposed. A data sequence of optical pulses with 2-ns duration was efficiently time-reversed.


Journal ArticleDOI
Abstract: A numerical experiment is carried out to study the focusing of a low-frequency (100–300 Hz) sound field in a shallow-water acoustic waveguide typical of an oceanic shelf. Focusing with the use of time reversal of broadband acoustic signals, which is called time reversal mirror (TRM) of waves, is considered along with focusing by phase conjugation (PC) of a monochromatic sound field. It is demonstrated that, in the case of focusing by the TRM method in the waveguide of interest, it is sufficient to have a single source-receiving element. The use of a vertical array improves the quality of focusing. The quality achieved in the latter case proves to be approximately the same as that achieved in the case of focusing by phase conjugation of a monochromatic field at a frequency identical to the carrier frequency of the broadband signals. It is also shown that, in a range-independent waveguide, intense surface waves considerably reduce the quality of focusing. This effect is most pronounced in the case of using phase conjugation.

Journal ArticleDOI
TL;DR: N numerically investigate the possibility of observing analogous effects in the optical domain using small cylindrical scatterers of realistic dielectric materials combined with an enclosing optical phase conjugate mirror in two-dimensional geometries.
Abstract: Recent work has demonstrated sub-diffraction limited focusing using time-reversal mirrors and sources in scattering media at microwave frequencies. We numerically investigate the possibility of observing analogous effects in the optical domain using small cylindrical scatterers of realistic dielectric materials combined with an enclosing optical phase conjugate mirror in two-dimensional geometries. Such focusing is possible but appears not to significantly exceed the focusing available from an equivalent homogenized material, and is highly sensitive to precise scatterer configuration.