两种方法实现对掺镱光纤放大器的相位校正

 在光纤激光器阵列的相干合成技术中，主振荡并联放大器（MOPA）方案最关键的技术是对光纤放大器进行相位控制与校正。本文用两种方法分别对掺镱光纤放大器进行了相位控制与校正。一种是爬山法，通过自动寻优的方式不断改变相位调制器控制电压，使系统输出保持在干涉最强处；另一种是外差法，通过实时探测和校正光路中相位的变化，确保输出光束的相位一致。实验系统中主振荡激光器的波长为1 083 nm，输出功率0~100 mW连续可调。光纤相位调制器是铌酸锂相位调制器。光纤放大器输出功率0~1 W连续可调，整个光路为全保偏光路。爬山法系统的工作频率为100 kHz，控制精度为λ/10；外差法系统的移频量为40 MHz，精度优于λ/20。在两类闭环控制过程中，铌酸锂相位控制器都很好地实现了光纤放大器的相位校正。该工作为实现光纤激光器阵列的相干合成打下实验基础。

Two methods to realize phase controlling of ytterbium fiber amplifiers

In the field of fiber laser coherent combining, phase controlling of ytterbium fiber amplifiers is the most difficult technology in the Master Oscillator-Power Amplifier scheme. Two methods to realize phase controlling of ytterbium fiber amplifiers are studied. One is “climbing hill”, which can optimize the control voltage automatically and the other is “heterodyne detection”, which can realize real-time detection and correction of the phase change. In the experiments, the wavelength of the master oscillator is 1 083 nm and the output power is between 0~100 mW. Phase noises are controlled by LiNO3 phase modulator. The output power of ytterbium fiber amplifiers is between 0~1 W. The fibers are polarizedly maintained. The “climbing hill” control system works at 100 kHz and the control