Topic
Phase conjugation
About: Phase conjugation is a research topic. Over the lifetime, 3694 publications have been published within this topic receiving 49099 citations.
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TL;DR: The characteristics of a new high-gain photorefractive polymer composite with a PNP chromophore with intensity dependence of TWC gain are investigated and higher diffraction order and forward phase conjugation in a TWC geometry are observed and explained.
Abstract: The characteristics of a new high-gain photorefractive polymer composite with a PNP chromophore are investigated. Competition between beam fanning and two-wave coupling (TWC) is predicted and verified experimentally. The intensity dependence of TWC gain is studied. Higher diffraction order and forward phase conjugation in a TWC geometry are observed and explained.
20 citations
TL;DR: The saturation behavior of band-gap resonant optical nonlinearity is studied by degenerate four-wave mixing experiments at 10.6 microm in HgCdTe over a wide range of laser intensities to form a theory based on the saturation of the interband absorption at the pump frequency resulting from state blocking.
Abstract: The saturation behavior of band-gap resonant optical nonlinearity is studied by degenerate four-wave mixing experiments at 10.6 μm in HgCdTe over a wide range of laser intensities. The reflectivity clips at a constant level when the laser intensity is increased above 100 W/cm2, and the corresponding effective third-order nonlinear susceptibility drops as the inverse of the laser intensity. A theory based on the saturation of the interband absorption at the pump frequency resulting from state blocking is presented and agrees well with the experiment.
20 citations
TL;DR: In this article, a DMD-based optical design was proposed to achieve high-speed binary phase modulation at the rate of 20 kHz in two-photon excitation fluorescence applications.
Abstract: The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation, or patterned photostimulation. For most of these applications, it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.
20 citations
TL;DR: In this article, it was shown that cascaded χ(2) processes can make a substantial contribution to the phase-conjugate signal in a material without inversion symmetry.
Abstract: The process of degenerate four-wave mixing in a material with a nonzero second-order susceptibility is theoretically investigated. The contributions by cascaded second-order processes to the overall third-order response are calculated by solution of the coupled-wave equations, assuming plane input fields. The driven coupling fields at frequencies 2ω = ω + ω and 0 = ω − ω, created by the second-order polarization, are very far from phase matching and are therefore calculated with proper boundary conditions without the use of the slowly varying envelope approximation. As a consequence of the large phase mismatch of the generated second-harmonic wave, the dominant pathway for cascading in degenerate four-wave mixing is via the generated dc field. With LiNbO3, KNbO3, and KTP as explicit numerical examples it is shown that cascaded χ(2) processes can make a substantial contribution to the phase-conjugate signal in a material without inversion symmetry.
20 citations
TL;DR: The results of an experimental study of the effects of laser coherence on the operation of the double phase-conjugate mirror using barium titanate as the nonlinear medium are significant to laser phase-locking applications where changes in the coupling intensity can affect the quality of phase locking.
Abstract: We present the results of an experimental study of the effects of laser coherence on the operation of the double phase-conjugate mirror using barium titanate as the nonlinear medium. In our experiment the two input beams that drive the interaction originate from a single helium–neon laser, and the degree of coherence between the input beams at the crystal is varied through the use of a time-dependent phase delay in one of the beam paths. As the two input beams make the transition from being mutually incoherent to mutually coherent, the phase-conjugate reflectivity decreases dramatically and becomes unstable. These results are significant to laser phase-locking applications where changes in the coupling intensity can affect the quality of phase locking.
20 citations