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: A commercially available sound transducer is employed to generate two sound foci in parallel, doubled the wavefront measurement speed, and reduced the mechanical scanning steps of the sound Transducer to half.
Abstract: Ultrasound pulse guided digital phase conjugation has emerged to realize fluorescence imaging inside random scattering media. Its major limitation is the slow imaging speed, as a new wavefront needs to be measured for each voxel. Therefore 3D or even 2D imaging can be time consuming. For practical applications on biological systems, we need to accelerate the imaging process by orders of magnitude. Here we propose and experimentally demonstrate a parallel wavefront measurement scheme towards such a goal. Multiple focused ultrasound pulses of different carrier frequencies can be simultaneously launched inside a scattering medium. Heterodyne interferometry is used to measure all of the wavefronts originating from every sound focus in parallel. We use these wavefronts in sequence to rapidly excite fluorescence at all the voxels defined by the focused ultrasound pulses. In this report, we employed a commercially available sound transducer to generate two sound foci in parallel, doubled the wavefront measurement speed, and reduced the mechanical scanning steps of the sound transducer to half.
17 citations
TL;DR: Combining double-phase conjugation with various coherent amplifiers leads to an amplified beam (forward or conjugated) derived from a local laser but bearing the transversal phase pattern of a received signal beam from a remote laser.
Abstract: Combining double-phase conjugation with various coherent amplifiers leads to an amplified beam (forward or conjugated) derived from a local laser but bearing the transversal phase pattern of a received signal beam from a remote laser. We suggest several uses in optical communication through a distorting atmosphere.
17 citations
TL;DR: This review gives accounts of the effort of imaging through turbid media using harmonic holographic phase conjugation, which provides a unique opportunity for imaging through a turbid medium.
Abstract: The ability to see inside the body noninvasively is indispensable in modern biology and medicine. Optical approaches to such abilities are of rapidly growing interest because of their nonionizing nature and low cost. However, the problem of opacity due to the optical turbidity of tissues must be addressed before optical means become practical. Harmonic holography amalgamates the capability of holographic phase conjugation with the contrast-forming mechanism of second-harmonic generation, which provides a unique opportunity for imaging through a turbid medium. In this review we give accounts of the effort of imaging through turbid media using harmonic holographic phase conjugation.
17 citations
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.
17 citations
TL;DR: In this article, the dispersion of the Kerr susceptibility is measured in a degenerate four-wave mixing experiment, and it is shown that the nonlinear response is quite different for experimental and commercial glasses.
Abstract: We report results on optical phase conjugation in experimental CdSSe-doped glasses close to a quantum-confined resonance. The dispersion of the Kerr susceptibility is measured in a degenerate four-wave mixing experiment, and it is shown that the nonlinear response is quite different for experimental and commercial glasses. In particular, for the former the spectral dispersion of the nonlinearity exhibits an intensity dependence. The various results can be explained by a competition between three mechanisms corresponding to the saturation of the electronic transitions involved (volume and surface states) by taking into account the efficient trapping of carriers into deep impurity levels.
17 citations