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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 novel configuration has been developed for performing degenerate four-wave mixing experiments using optical phase conjugation from stimulated Brillouin scattering in a cell that greatly simplifies DFWM experiments by relaxing alignment constraints and sensitivities to index-of-refraction gradients in the flow.
Abstract: A novel configuration has been developed for performing degenerate four-wave mixing (DFWM) experiments using optical phase conjugation from stimulated Brillouin scattering in a cell. The typical geometry for DFWM requires that two pump beams counterpropagate through the measurement volume, which is accomplished either by splitting off a portion of the beam and directing it in from the opposite direction or reflecting the first pump beam back onto itself. In both approaches it can be difficult to maintain alignment between the counterpropagating pump beams, particularly in combustion systems that present thermal and density gradients. DFWM has been demonstrated for OH in a flame by using counterpropagating pump beams that are phase conjugate. The optical phase conjugation is achieved by focusing the first pump beam into a cell containing hexane, which produces a counterpropagating beam through stimulated Brillouin scattering. This approach greatly simplifies DFWM experiments by relaxing alignment constraints and sensitivities to index-of-refraction gradients in the flow.
20 citations
TL;DR: The focusing and phase conjugation of photon echoes was observed in Na vapor and the echo center of curvature or focus followed from the phase φE(r) =2φ2 (r)−φ1( r) in the Na cell.
Abstract: The focusing and phase conjugation of photon echoes was observed in Na vapor. If the radius of curvature of the first pulse was R1 and the second pulse R2, the radius of curvature of the echo was given by 1/RE=2/R2−1/R1 and the echo center of curvature or focus followed from the phase φE(r) =2φ2(r)−φ1(r) in the Na cell.
20 citations
TL;DR: This work generalizes the time-resolved technique to reconstruct the spatially varying reflectance of shapes hidden by angle-dependent diffuse layers, a noninvasive method of imaging three-dimensional objects without relying on coherence.
Abstract: Imaging through complex media is a well-known challenge, as scattering distorts a signal and invalidates imaging equations. For coherent imaging, the input field can be reconstructed using phase conjugation or knowledge of the complex transmission matrix. However, for incoherent light, wave interference methods are limited to small viewing angles. On the other hand, time-resolved methods do not rely on signal or object phase correlations, making them suitable for reconstructing wide-angle, larger-scale objects. Previously, a time-resolved technique was demonstrated for uniformly reflecting objects. Here, we generalize the technique to reconstruct the spatially varying reflectance of shapes hidden by angle-dependent diffuse layers. The technique is a noninvasive method of imaging three-dimensional objects without relying on coherence. For a given diffuser, ultrafast measurements are used in a convex optimization program to reconstruct a wide-angle, three-dimensional reflectance function. The method has potential use for biological imaging and material characterization.
20 citations
TL;DR: In this article, a four-wave mixing by gain saturation in a laser-pumped Ti:sapphire (Ti3+:Al2O3) amplifier is demonstrated for the first time.
Abstract: Four-wave mixing by gain saturation in a laser-pumped Ti:sapphire (Ti3+:Al2O3) amplifier is demonstrated for the first time to our knowledge. Small-signal gain in excess of 250 has been obtained by intense laser pumping at 532 nm, resulting in observed four-wave mixing energy reflectivity as high as 360% for nanosecond pulses at 780 nm.
20 citations
TL;DR: In this paper, a XeCl laser system has been used to investigate stimulated Brillouin scattering (SBS) cyclohexane and methanol with laser radiation of spectral width Delta nu /sub p/ much larger than the bandwidth of the excited acoustic wave.
Abstract: A XeCl laser system has been used to investigate stimulated Brillouin scattering (SBS) cyclohexane and methanol with laser radiation of spectral width Delta nu /sub p/ much larger than the bandwidth of the excited acoustic wave Delta nu /sub a/. The reflectivity and the phase conjugation (PC) fidelity of the SBS reflector versus pump intensity and bandwidth have been measured. It is shown experimentally that the PC fidelity and the reflectivity are strongly dependent on the pump spectral width and intensity. However, the experimental results show that the use of a liquid SBS reflector is still effective for correcting the spatial aberrations of laser radiation with Delta nu /sub p/ approximately=30 Delta nu /sub a/ in a double-pass amplifier. >
20 citations