Ba(NO3)2晶体受激拉曼散射的角度分布和脉冲压缩

报道了利用重复频率为30 Hz，波长为532 nm 的Nd∶YAG倍频激光单次通过抽运硝酸钡（Ba(NO3)2）晶体（晶体由水溶液降温法生长，长度为48 mm，横截面为10 mm×10 mm），获得高效率的一阶（563 nm），二阶（599 nm）和三阶（639 nm）斯托克斯光的实验结果.硝酸钡晶体沿着［110］晶轴方向切割.观测到一、二、三阶斯托克斯光呈锥形环分布，一、二、三阶斯托克斯光的散射外边缘与抽运光轴线间的夹角大小分别为1.7°，3.5°，5.0°.同时也观测到Ba(NO3)2的SRS角度分布与抽运光强度无关.定性分析认定,Ba(NO3)2的SRS角度分布主要是由相位匹配过程决定的.测得抽运光、一、二、三阶斯托克斯光的脉宽分别为11.6 ns，9.8 ns，8.4 ns和4.5 ns.当抽运光功率密度约为150 W/cm2时，获得一、二、三阶斯托克斯光的最大光光转换效率，分别为33.5%，8.8%和3.4%. 此外，由于晶体中的热沉积效应，观察到了Ba(NO3)2晶体的SRS转换效率饱和现象.

Angular Distribution and Pulse Compression of Stimulated Raman Scattering in Ba(NO3)2 Crystal

The high-efficiency SRS in barium nitrate (Ba(NO3)2) crystal was obtained pumped by a Q-switched Nd:YAG laser (532 nm) operated at 30 Hz.In the forward scattered direction, the first (563 nm),second (599 nm) and third (639 nm) Stokes pulses were presented,the radiation fields of which had cone structures with the scattered angles of 1.7°,3.5° and 5.0°,respectively.Furthermore,it was pointed out that the angular distribution of Stokes radiation was independent of the pump intensity in this work.The results show that the angular distributions of SRS in Ba(NO3)2 crystals are mainly attributed to the phase matched process.The pulse widths of the pump, first, second and third Stokes pulses were measured to be 11.6 ns,9.8 ns,8.4 ns and 4.5 ns, respectively.This indicates that SRS in Ba(NO3)2 crystals can provide the possibility of effective pulse compression and increase of peak pulse intensity.With the pump intensity of about 150 W/cm2, the maximum conversion efficiencies of the first,second and third Stokes pulses were 23.5%,8.8% and 3.4%,respectively.Moreover,the saturation phenomenon of SRS efficiency was experimentally observed,which was due to the thermal loading in the Ba(NO3)2 crystal.