7 October 1996 Two-beam coupling in liquids via stimulated Rayleigh-wing scattering
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Transient energy transfer or two-beam coupling is demonstrated in CS2 and other transparent Kerr liquids using frequency chirped, 17 picosecond (HW1/eM) 532 nm pulses with several polarization combinations. As the temporal delay between pulses in a standard pump-probe geometry is varied within the coherence time, the first pulse always loses energy while the second pulse gains this energy. Scattering from phase gratings can lead to coherent energy coupling only if the nonlinearity has a finite relaxation time. This two-beam coupling in Kerr media such as CS2 is associated with stimulated Rayleigh-wing scattering (SRWS). The frequency difference needed for beam coupling can be achieved with chirped pulses or with short pulses in nonlinear materials if irradiance dependent phase shifts are being developed during the laser pulse due to self and cross-phase modulation. Here we consider the interaction between linearly chirped pulses obtained from our modelocked, Q-switched Nd:YAG laser. This leads to an energy transfer linearly proportional to irradiance, so that the signal can be observed at irradiances lower than those needed for induced phased modulation. The measurements are performed on CS2 but the results are valid for any Kerr liquid that has a nonlinear index of refraction with a relaxation time on the order of the laser pulse width. We demonstrate that the interaction follows the polarization dependence of SRWS. The only parameters needed for the theoretical fittings are the nonlinear index n2, its relaxation time and the linear chirp of the laser pulse. The first two are well known for CS2 and the laser chirp is independently measured using first and second order autocorrelations.
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Aristide C. Dogariu, Aristide C. Dogariu, Tie Jun Xia, Tie Jun Xia, David J. Hagan, David J. Hagan, Ali A. Said, Ali A. Said, Eric W. Van Stryland, Eric W. Van Stryland, Nicolaas Bloembergen, Nicolaas Bloembergen, } "Two-beam coupling in liquids via stimulated Rayleigh-wing scattering", Proc. SPIE 2853, Nonlinear Optical Liquids, (7 October 1996); doi: 10.1117/12.253466; https://doi.org/10.1117/12.253466

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