单纵模Nd:YAG激光泵浦H_2气中的受激喇曼散射  

Stimulated Raman Scattering in H_2 Pumped by a Single Longitudinal Mode Nd:YAG

作　　者：花晓清[1] 冷静[1] 杨何平[1] 沙国河[1] 张存浩[1] 

机构地区：[1]中国科学院大连化学物理研究所分子反应动力学国家重点实验室,大连116023

出　　处：《Chinese Journal of Chemical Physics》2005年第6期861-866,共6页化学物理学报（英文）

基　　金：ProjectsupportedbyNKBRSF(G1999075303).

摘　　要：用单纵模Nd:YAG激光(波长1.06μm,脉宽9ns,线宽0.003cm-1)泵浦氢气中的受激喇曼散射,产生很强的后向一级斯托克斯.当泵浦能量为120mJ,压力为1.5MPaH2时,后向和前向喇曼的光子转化效率分别为66%和15%,而在4MPa时两个数值分别为46%和39%.由于后向喇曼与前向喇曼和泵浦光的传播方向相反,二者的相互竞争产生了张弛振荡,使得后向和前向喇曼的时间波形都分裂为两个峰,后向喇曼的两个峰都被压窄到1ns,使峰值功率达到了泵浦光功率的二倍,这在前向喇曼是不可能的.而且后向喇曼的光束质量要大大优于泵浦光和前向喇曼的光束质量,在4MPaH2和脉冲重复频率为10Hz时,喇曼过程的放热使前向喇曼的光束质量变坏,但对后向喇曼的光束质量影响不大.计算表明,该实验条件下受激喇曼过程没有达到稳态,所有实验结果都可以而且只能用相关的瞬态受激喇曼理论解释.Strong backward first Stokes （BS） in H2 is observed when a single longitudinal mode fundamental frequency Nd： YAG laser （ 1.06μm, pulsed width about 9 ns, linewidth 0. 003 cm^-1 ） is used as the pump source. Using a pump energy of 120 mJ, photon conversion efficiency of FS and BS was determined to be 66% and 15% respectively in 1.5 MPa H2, while in 4.0 MPa H2 the respective values are 46% and 39%. Due to their propagation in opposite directions, there is tension between FS and BS, which leads to a relaxation of the oscillation that splits both FS and BS pulses into two peaks, with the BS pulses being narrowed to about 1 ns. Surprisingly, the BS peak power reaches twice that of the pump, which can never happen in the FS case. Furthermore, the beam quality of BS is much better than that of both FS and pump. At 4 MPa of H2 pressure and a 10 Hz cycle rate, the thermal release of the Raman process deteriorates the FS beam quality, without noticeably affecting that of BS. According to this calculations, within the present experimental conditions, the stimulated Raman scattering process does not reach the steady state. Because of this, all of the experimental results can be explained explained by a related transient state, theory of stimulated Raman scattering.

关 键 词：ND:YAG激光 H2气中受激喇曼散射 喇曼脉冲张弛振荡 

分 类 号：O437.3[机械工程—光学工程]