Showing papers on "Phase conjugation published in 1996"
TL;DR: In this article, a new method was proposed to compensate exactly for both chromatic dispersion and self-phase modulation in a transmission fiber, where the light intensity changes due to fiber loss and amplifier gain.
Abstract: We propose a new method to compensate exactly for both chromatic dispersion and self-phase modulation in a transmission fiber, where the light intensity changes due to fiber loss and amplifier gain. This method utilizes optical phase conjugation (OPC). The pulse shape is precompensated before OPC by transmission through a fiber with large dispersion. A computer simulation demonstrates effective compensation for waveform distortion in a 40 Gb/s NRZ intensity-modulated light transmission.
258 citations
TL;DR: A dispersive medium with a negative nonlinear refractive-index coefficient is proposed as a way to compensate for the dispersion and the nonlinear effects resulting from pulse propagation in an optical fiber to allow for increased bit rates.
Abstract: We propose the use of a dispersive medium with a negative nonlinear refractive-index coefficient as a way to compensate for the dispersion and the nonlinear effects resulting from pulse propagation in an optical fiber. The undoing of pulse interaction might allow for increased bit rates.
123 citations
TL;DR: A holographic grating is written into a photorefractive erasable holographic member and a light beam having a first wavelength which includes the joint power spectrum of a pair of joint images to be correlated is directed at the photoreFractive member to partially erase the grating.
Abstract: A holographic grating is written into a photorefractive erasable holographic member and a light beam having a first wavelength which includes the joint power spectrum of a pair of joint images to be correlated is directed at the photorefractive member to partially erase the grating. A phase conjugate signal from the partially erased grating is then readout and Fourier transformed to produce the correlation output spots.
42 citations
TL;DR: Backward stimulated Brillouin scattering was used to control the growth of amplified spontaneous emission (ASE), reducing the unwanted emission in a pulse-amplified cw Ti:sapphire laser system from 22% to less than 1 x 10(-4) in the final output.
Abstract: Backward stimulated Brillouin scattering was used to control the growth of amplified spontaneous emission (ASE), reducing the unwanted emission in a pulse-amplified cw Ti:sapphire laser system from 22% to less than 1 × 10−4 in the final output. Suppression of ASE substantially improved the spectral quality of the laser and broadened the range over which the laser is useful. The output duration was compressed, but the pulse remained nearly transform limited.
38 citations
TL;DR: A spectral-inversion technique with no wavelength shift is presented that utilizes a novel four-wave mixing scheme named the optical parametric loop mirror that eliminates both the input signal wave and the nondegenerate pump waves from the FWM wave generated at the signal wavelength.
Abstract: A spectral-inversion technique with no wavelength shift is presented that utilizes a novel four-wave mixing (FWM) scheme named the optical parametric loop mirror. This scheme eliminates both the input signal wave and the nondegenerate pump waves from the FWM wave generated at the signal wavelength. The compensation of waveform distortion caused by fiber chromatic dispersion is successfully demonstrated by the proposed method.
32 citations
TL;DR: It is demonstrated that recording thick holographic phase gratings in photorefractive polymers can lead not only to very efficient Bragg diffraction but also to rather strong diffraction into non-Bragg orders.
Abstract: We demonstrate that recording thick holographic phase gratings in photorefractive polymers can lead not only to very efficient Bragg diffraction but also to rather strong diffraction into non-Bragg orders. We show that this effect has features drastically different from those of Raman–Nath diffraction on thin gratings. We compare the experimental results with a model based on the theory of dynamic self-diffraction in a photorefractive medium. Applications of this effect in devices for optical image processing are proposed.
25 citations
TL;DR: It is experimentally demonstrated that wave-front reversal of picosecond optical signals can be efficiently achieved with low-gain parametric amplification with the use of a KTP crystal.
Abstract: Revisiting the pioneering work of Avizonis et al. [Appl. Phys. Lett. 31, 435 (1977)], we experimentally demonstrate that wave-front reversal of picosecond optical signals can be efficiently achieved with low-gain parametric amplification. The use of a KTP crystal permits forward phase conjugation of radiation with high divergence (40 mrad) and a broad spectrum (20 nm). The potential application of this technique to compensate for the group-velocity dispersion of standard optical fibers in the 1.55-μm window is discussed.
24 citations
TL;DR: In this paper, optical phase conjugation via stimulated Brillouin scattering (OPC-SPS) in the presence of a moderately high magnetostatic field is studied in centrosymmetric semiconducting crystals under a parabolic approximation.
Abstract: Based upon the density matrix formulations of nonlinear optical susceptibility, optical phase conjugation via stimulated Brillouin scattering (OPC-SPS) in the presence of a moderately high magnetostatic field is studied in centrosymmetric semiconducting crystals under a parabolic approximation. The magnetostatic field B has a twofold contribution to the coherent radiation - semiconductor interaction through the formation of discrete Landau levels and the sharpening of the density-of-states. Numerical estimations made for an InSb sample at low temperature irradiated by a 5.5 to 6.0 m CO laser reveal enhancement in the value of Brillouin susceptibility in the presence of the magnetostatic field B. This in turn lowers the threshold intensity required for the onset of OPC-SBS. A considerably high reflectivity is obtained when B is increased from 1 to 4.02 T. For experimental observation of OPC-SBS as described in the paper, it may be stressed that the polarization of the laser should be properly determined so that the crystal is effectively centrosymmetric.
22 citations
22 citations
TL;DR: Self-pumped phase conjugation is observed retroref lected by a BaTiO(3) crystal and the conjugate character of the pulses is demonstrated with the distorter method.
Abstract: Self-pumped phase conjugation is generally believed to be attributed to degenerate four-wave mixing. Accordingly, the phenomenon requires the existence of three waves at certain interaction regions for the excitation of the fourth one. Although this condition is not satisfied by a train of femtosecond pulses with a repetition rate of 110 MHz, we have observed self-pumped conjugate pulses retroreflected by a BaTiO3 crystal. The conjugate character of the pulses is demonstrated with the distorter method.
20 citations
TL;DR: In this paper, a high reflectivity (up to 670%) widebandwidth ( up to 230 MHz) phase-conjugate mirror was constructed using backward four-wave mixing with continuous-wave pump beams in a 2mm potassium vapor cell.
Abstract: We report on a high‐reflectivity (up to 670%) wide‐bandwidth (up to 230 MHz) phase‐conjugate mirror formed using backward‐four‐wave mixing with continuous‐wave pump beams in a 2‐mm potassium vapor cell. The reflectivities and bandwidths are significantly larger than have been measured previously, and the bandwidth is ten times greater than is predicted theoretically. The reflectivity‐bandwidth product is more than an order of magnitude improvement over those previously achieved with other continuous‐wave phase‐conjugate systems.
TL;DR: In this article, an enhancement of the diffraction efficiency of holographic gratings in Bi12Ti0.76V0.24O20 crystals by a factor of almost 40 is obtained after recording by application of an external dc electric field and illumination with a spatially homogeneous light beam.
Abstract: An enhancement of the diffraction efficiency of holographic gratings in Bi12Ti0.76V0.24O20 crystals by a factor of almost 40 is obtained after recording by application of an external dc electric field and illumination with a spatially homogeneous light beam. The enhancement increases with increasing applied field, larger spatial frequency, and longer writing time of the holographic grating, and with intensity of the homogeneous illumination. A theoretical description of the enhancement effect is proposed, assuming a modulated photoconductivity, which is generated by a strongly modulated concentration of photorefractive traps or donors.
11 Apr 1996
TL;DR: In this article, phase conjugation by SBS (stimulated Brillouin scattering) is a powerful and simple tool to increase the beam quality of high power lasers up to the diffraction limit.
Abstract: Phase conjugation by SBS (stimulated Brillouin scattering) is a powerful and simple tool to increase the beam quality of high power lasers up to the diffraction limit. Master oscillator and power amplifier systems with Nd:YAlO as active medium were realized with an average output power up to 210 watts at 1.08 micrometer in a near diffraction limited beam. Also Nd:YAG-oscillators with phase conjugating mirrors were realized with an average output power up to 17 watt and high beam quality. In the UV range, excimer oscillators with SBS mirrors deliver the same or better beam quality than conventional plane-plane resonators in 3 times shorter pulses. Excimer oscillator-amplifier arrangements have been realized with SBS mirrors. SBS mirrors for the visible and ultraviolet spectral range are well characterized. First experiments for an ordered passive fiber bundle with an SBS mirror show the possibilities and limitations to improve the beam quality of fiber bundle amplifies or even oscillators.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, the authors present results of numerical simulations of incomplete phase conjugation of a beam aberrated by a thin phase screen, and show that when the phase congruation is incomplete, introduction of an aberrator can lead to an improvement in the system resolution.
Abstract: We present results of numerical simulations of incomplete phase conjugation of a beam aberrated by a thin phase screen. We find good agreement with a previously developed theory for phase screens with Gaussian autocorrelation functions and investigate some regimes in which the theory is not valid. We show that when the phase conjugation is incomplete, introduction of an aberrator can lead to an improvement in the system resolution.
TL;DR: In this paper, spatially nondegenerate four-wave mixing in a broad-area laser diode that acts as a fast phase conjugate mirror with nanosecond response times and high efficiencies was reported.
Abstract: We report spatially nondegenerate four‐wave mixing in a broad‐area laser diode that acts as a fast phase conjugate mirror with nanosecond response times and high efficiencies. Phase conjugate reflectivities were found to depend strongly on the bias current of the broad‐area laser diode. Operating the laser diode in an injection‐locked regime above the lasing threshold gave phase conjugate reflectivities as high as 165%.
TL;DR: Optical phase conjugation in a bulk SOA has been optimized both under static and dynamic conditions in this article, which leads to a compromise between conversion efficiency and signal-to-background (S/B) ratio.
Abstract: Optical phase conjugation (OPC) in a bulk SOA has been optimized both under static and dynamic conditions. Conjugation with gain has been obtained. Dynamic optimization leads to a compromise between conversion efficiency and signal-to-background (S/B) ratio, providing that the modulated signal is kept a minimum of 5 dB weaker than the pump to avoid detrimental saturation effects. Transparent 10-Gb/s phase conjugation with extinction ratio around 20 dB at moderate power levels is reported.
TL;DR: In this paper, the application of biological photochrome bacteriorhodopsin (bR) films for real-time image processing is described; bR exhibits strong polarization-sensitive phase conjugation.
TL;DR: In this article, a single-rod neodymium amplifier with 140 W average output power and nearly diffraction-limited beam is described, and the beam quality can be significantly improved using phase-conjugating mirrors based on stimulated Brillouin scattering.
Abstract: For pumping XUV plasma light sources with solid-state lasers and also for micromaterial processing, high beam quality and output power as well as simplicity of the pump lasers are crucial. The beam quality of high-power solid-state lasers can be significantly improved using phase-conjugating mirrors based on stimulated Brillouin scattering (SBS). Hence, SBS phase conjugation may prove one of the key technologies in this field. We describe a single-rod neodymium amplifier with 140 W average output power and nearly diffraction-limited beam. Because of automatic compensation of the thermal lensing by SBS phase conjugation, the output power can be tuned without changing the beam profile.
TL;DR: In this article, a novel technique for narrowing the linewidth of a single laser diode using photorefractive phase conjugate feedback is presented, and the behavior of this system can be modeled by adapting the previously developed theory to include the phase constraints of the phase-constrained external cavity.
Abstract: A novel technique for narrowing the linewidth of a single laser diode using photorefractive phase conjugate feedback is presented. The behavior of this system can be modeled by adapting the previously developed theory to include the phase constraints of the phase conjugate external cavity. The experiments show excellent agreement with the model. This technique produces a stable, narrow linewidth in a semiconductor laser. The comparison to the conventional case is discussed.
TL;DR: In this article, the authors demonstrated stimulated Brillouin scattering phase conjugation in a hollow glass lightguide filled with CS 2, where the SBS threshold and reflectivity were unchanged with average input powers up to 20 W.
18 Sep 1996
TL;DR: In this paper, the photorefractive beam combiner was used for optical detection of ultrasonic signals based on photore-fractive effect and two techniques used the wavefront adaptation properties of photore fractive effect.
Abstract: We present and describe two techniques used for optical detection of ultrasonic signals based on the photorefractive effect. These techniques used the wavefront adaptation properties of the photorefractive effect. In the photorefractive beam combiner, a local oscillator matched to the signal wavefront is created, leading to an homodyne detection system having a large etendue. In the double phase conjugate heterodyne detection system the signal beam wavefront is cleaned by a double phase conjugate mirror and transformed in a plane wave that is sent on a classical heterodyne detection system. Both systems are characterized and used to detect ultrasound.
TL;DR: In this paper, the phase conjugation of a laser beam aberrated by a thin random-phase screen was investigated when the wave front is incompletely sampled by the PCM.
Abstract: We investigate phase conjugation of a laser beam aberrated by a thin random-phase screen when the wave front is incompletely sampled by the phase conjugate mirror (PCM). We derive expressions for the average intensity after a double pass of the phase screen both when the PCM is aperture limited and when it is limited by its number of spatial modes.
TL;DR: A 4Pi confocal system that incorporates a phase-conjugate mirror into the system to solve the alignment problem and automatically correct the spherical aberration associated with the conventional 4Pi Confocal system when observing a thick sample is proposed.
Abstract: We propose a 4Pi confocal system that incorporates a phase-conjugate mirror into the system to solve the alignment problem and automatically correct the spherical aberration associated with the conventional 4Pi confocal system when observing a thick sample. The proposed system is experimentally verified by use of cerium-doped barium titanate crystal as the phase-conjugate mirror. The full width of the central peak is ∼0.15 μm. We also theoretically verify the advantage of automatic correction of the spherical aberration by calculating the intensity distribution at the focal spot.
Proceedings Article•
02 Jun 1996TL;DR: In this paper, the technique of optical phase conjugation is used to reconstruct a laser beam that has been aberrated on passing through a distorting medium, producing a time-reversed replica of the original beam.
Abstract: Summary form only given. The technique of optical phase conjugation can be used to reconstruct a laser beam that has been aberrated on passing through a distorting medium. Reflection from a phase-conjugate mirror (PCM) produces a time reversed replica of the aberrated beam. The aberrations are removed when this phase-conjugate beam propagates back through the distorting medium, producing a time-reversed replica of the original beam.
TL;DR: In this paper, the authors proposed a novel scheme for implementing optical phase conjugation (OPC) by cascading transverse second-harmonic and difference-frequency generation in a vertical cavity.
Abstract: We propose a novel scheme for implementing optical phase conjugation (OPC) by cascading transverse second-harmonic and difference-frequency generation in a vertical cavity. We propose to achieve phase conjugation in the pump and input-output two-waveguide structure. For a symmetric waveguide structure, the structure can be used as an optical phase conjugate mirror. For a realistic structure based on III–V semiconductor materials, a pump power per unit waveguide of 0.74 W μm-1 is required to reach a conversion efficiency of ∼9.4%. Combined with another phase-conjugate mirror, the reflectivity of the proposed phase-conjugate mirror can be efficiently modulated by control of the pump power. For an asymmetric waveguide structure, a gain is predicted. In addition, by cascading second-harmonic generation (SHG) and parametric oscillation, we propose to use the same structure as a waveguide coupler. There is a threshold to achieve coupling.
TL;DR: In this article, the frequency stable, narrow linewidth oscillation of a 638 nm AlGaInP diode laser was achieved with an external photorefractive BaTiO3 phase conjugator in a novel configuration.
Abstract: Frequency‐stable, narrow linewidth oscillation of a 638 nm AlGaInP diode laser has been achieved with an external photorefractive BaTiO3 phase conjugator in a novel configuration. The mechanism of the phase conjugation in this configuration is the stimulated photorefractive backscattering process with the measured phase‐conjugate reflectivity of <1.8×10−3%. With this new phase‐conjugate feedback method, the laser linewidth was reduced to ∼0.1 nm (within the resolution limit of the spectrum analyzer used) and the oscillation frequency was highly stabilized, while it was impossible with a conventional cat conjugator.
TL;DR: In this paper, two-beam coupling configurations were employed to obtain the phase conjugate image and edge extraction of an object using photorefractive KNbO 3 : Fe.
Abstract: Two-beam coupling configurations are employed to obtain the phase conjugate image and edge extraction of an object using photorefractive KNbO 3 : Fe. Also, the self-organization of a beam in the material into a hexagonal spot array is utilized to broadcast an input object to the location of each of the spots.