大频差双腔双频Nd:YAG激光器频差调谐方法与频差稳定技术研究

Tunable dual-frequency lasers with large frequency difference are of great scientific significance with the special research value in many fields such as interferometer for absolute distance，microwaves photonics and optical laser radar，etc. In this project an electro-optics birefringent filter consisting of an electro-optic crystal and a polarizing beam splitter is included in a diode-end-pumped Nd:YAG laser cavity, thus the p-and s-component of 1064nm laser light can be enforced to oscillate simultaneously in single longitudinal mode in the straight and right angle cavities，respectively. A beam of orthogonally and linearly polarized dual-frequency Nd:YAG laser at 1064nm can coaxially output from an external-cavity cube. The mode selection law of the electro-optics birefringent filter is theoretically studied，and the conditions of single longitudinal mode operation are investigated, and the law of simultaneous oscillation of two single longitudinal modes in two cavities is revealed through experimental study. Changing the transverse voltages applied to the electro-optic crystals, we experimentally study the law of frequency difference tuning and we can tune the frequency difference of the dual-frequency laser from 10GHz to 150GHz.Using the method of Pound-Drever-Hall frequency stabilization,We will stable the two single longitudinal modes resonant frequencys at the center frequency of the same F-P cavity. The stabilization of frequency difference is superior to 0.1ppm.The tunable two-cavity dual-frequency laser with large frequency difference will lay the foundation for high-precision absolute distance measrement,etc。

可调谐大频差双频激光器在绝对距离干涉测量、微波光电子和激光雷达等领域具有重要科学意义及研究价值。本项目拟用电光晶体和偏振分光棱镜组成电光双折射滤光片，将其置于LD端面泵浦Nd:YAG激光谐振腔内，使1064nm光波的p偏振分量和s偏振分量分别在一直线型和一直角型驻波谐振腔内同时以单纵模振荡输出，经腔外合光后即得到共线传播的正交线偏振双频激光。理论研究电光双折射滤光片的选模规律，探讨单纵模运转的稳定性条件，实验研究双腔单纵模同时振荡的规律；改变施加在电光晶体上的横向电压，实验研究双频激光的频差调谐规律，频差调谐范围达到10GHz～150GHz。采用Pound-Drever-Hall稳频方法，将两个单纵模激光频率稳定在同一个F-P参考频率处，实验研究双腔单纵模激光频率和频差稳定技术，双频激光频差稳定性优于0.1ppm。这种大频差可调谐双腔双频稳频激光器将为高精度绝对距离测量等应用奠定基础。

大频差可调谐双频激光器广泛应用于激光干涉测量和光学传感等领域。设计并研究了自然双折射双腔双频Nd:YAG激光器和电光双折射双腔双频Nd:YAG激光器，使1064nm激光p分量和s分量分别在直线腔和直角腔内同时以单纵模振荡，实现正交线偏振双频激光输出；通过调谐方解石晶片与腔轴的夹角和铌酸锂电光晶体上的电压，可使1064nm双频激光的频差分别在11.4GHz～168.6GHz和9GHz～132GHz范围内调谐，其最大频差接近Nd:YAG晶体的荧光线宽。设计了一种扭转模结构的双腔双频Nd:YAG激光器系统，研究了单腔Nd:YAG激光器纵模分裂现象和双腔双频Nd:YAG激光器的频差调谐特性，其最大频差均为1个纵模间隔。研制了双波长双频全固态激光器的样机。采用高精细度Fabry-Perot腔作为频率基准，设计了基于正交解调原理的双腔双频Nd:YAG激光器PDH稳频系统，其频率稳定性优于10-9。