用于795nm压缩光源的单频激光系统的优化设计

Optimal Design of Single-Frequency Laser System for 795 nm Squeezed Light Source

采用自制的795 nm连续单频可调谐钛宝石激光器抽运周期极化磷酸氧钛钾(PPKTP)晶体,通过外腔谐振倍频技术获得了功率为103 m W,倍频转换效率为39.6%、光束质量因子M2<1.43的397.5 nm紫光输出;与角度匹配的三硼酸铋(BIBO)晶体内腔倍频情况相比,紫光与光学参量放大器(OPA)的模式匹配效率由76%提高到了99%以上。同时,在平衡零拍探测系统中,通过在本底光光路中插入与OPA腔型相同的模式清洁器,使得本底光与信号光的空间模式完全相同,从而将两束光的干涉效率提高到了99%以上,提高了平衡零拍系统的探测效率。通过对自制的795 nm和397.5 nm单频激光系统的优化设计,使该光源满足了小型化795 nm连续变量压缩源样机研制的要求。

By using an extra-cavity-enhanced frequency doubler with a periodically poled KTi OPO4（PPKTP）crystal, which is pumped by a home-made continuous-wave single-frequency tunable Ti： sapphire laser at 795 nm wavelength, the 397.5 nm violet laser is obtained experimentally with the output power of 103 m W, conversion efficiency of 39.6%, and the beam quality factor M2〈1.43. Compared with the intracavity enhanced frequency doubling with the angle matched Bismuth Triborate（BIBO） crystal, the mode matching efficiency of the 397.5 nm lasing to the optical parametric amplifier（OPA） cavity is increased from 76% up to 99%. Meanwhile, in the balanced homodyne detection system, a mode cleaner with the same cavity parameters as OPA, is inserted into the local oscillator to make sure the local oscillator and the signal fields have the identical spatial modes. As a result, the interference efficiency of the two input fields is more than 99%, and the efficiency of the balanced homodyne detection system is improved. By optimizing the design of the 795 nm and 397.5 nm laser system, the laser source can meet the requirement of studying the compact continuous-variable squeezed light source at 795 nm.