体光栅能量振荡与脉冲分裂的研究

Study on the Energy Oscillation and Pulse Splitting in Volume Grating

基于修正的Kogelnik耦合波方程,研究了飞秒脉冲通过正弦型体光栅衍射后的动态衍射特性—能量振荡和脉冲分裂现象随光栅参数和读出脉冲参数的变化。结果发现,体光栅的折射率调制度和读出脉冲的中心波长对能量振荡的周期有影响,而体光栅的周期对能量振荡周期没有影响,但会影响脉冲波包中心连线与时间轴的夹角。通过双光束干涉、群速度和群时延对出现的现象进行了解释。在衍射后期,衍射脉冲分裂为双脉冲,双脉冲间隔与体光栅的厚度和折射率调制度有关,但与体光栅周期无关,通过光场传播的局域化特性对其进行了解释。

Based on the modified coupled-wave equations of Kogelnik, the dynamical diffraction properties, energy oscillation and pulse splitting of a sinusoidal volume holographic grating （VHG） illuminated by a femtoscond pulse with respect to the grating parameters and readout pulse parameters are studied. Result shows that the refractive index modulation of VHG and central wavelength of the readout pulse will affect the energy oscillation period, while the grating period has no effect on the energy oscillation period, but it will affect the angle between the line connected by centers of diffracted wave packets and the time axis. Based on group velocity and group delay, explanations on these phenomena are given. In the latter stage, diffracted pulse splits into two pulses, the pulse interval between them depends on the thickness and refractive index modulation of the VHG, and independent of the grating period, we explain it with the localization property of light field propagation.