Study On The Two Pulses Propagating In Normal Dispersive Media And Nonlinear Acoustic-optical Effect At Low-frequency

Our research includes two parts: one part, we study the question on the two pulses in the transverse x dimension propagating in normal dispersive nonlinear media. The other part, we discuss nonlinear acoustic-optical effect from liquid surface waves at low-frequency.The propagation of high-peak-power laser pulses in isotropic dispersive nonlinear media gives rise to strong nonlinear effects such as four-wave mixing, stimulated Raman processes, self-focusing and self-phase modulation which lead to strong modifications of the pulse characteristics. Many recent studies have shown that pulse splitting occurs in the normal dispersive media, when the pulse with power beyond the threshold for self-focusing. In other hand, if two high-peak-power pulses in the transverse x dimension propagate in dispersive nonlinear media, the interactions between pulses are interest and importance.In this paper, we take two pulses in the transverse x dimension into account. We calculated numerically several important phenomena when two pulses propagate in the isotropic normal dispersive nonlinear media. The numerical method includes some of linear and nonlinear term, such as group-velocity dispersion, third-order dispersion, diffraction, mixed space-time third-order terms, self-focusing and self-phase modulation.Through our numerical calculation, we obtained several useful results in our model. First, when the power of two pulses is just now beyond the lower intensity threshold, self-phase modulation and velocity dispersion split the pulses into two pulselets in time, a) when their relative phase is zero, there are no power transfer between the pulses, the pulses appear to attract each other, the intensity in the center region between the pulses is increase, b) when their relative phase is , there are no power transfer between the pulses too, the two pulses appear to repel each other, c) when their relative phase is /2, power transfers between the two pulses. One pulse's power is decrease. In the same time the other pulse's power is increase, which lead to the pulses split in both time and transverse space dimensions. Second, when two pulses intensities above the higher threshold, after the temporal pulse spitting occurs, pulses split in transverse space dimension too. Thus each pulses format two additional satellite peaks centered in the space dimension, the interactions consist in the two middle satellite peaks.In this paper, the other question we discuss is nonlinear acoustic-optical effect from liquid surface waves at low-frequency. Steady and high visible diffraction patterns with higher order maxima from liquid surface acoustic waves at low-frequency were obtained experimentally. Considering the high-order harmonic acoustic waves on liquid surface, the corresponding analytic expression of diffraction intensity pattern under the nonlinear condition was derived and theoretical results were compared with the experimental data. It was shown that they are well agreement.