主振荡功率放大器结构光纤激光相干合成系统对谱线需求的实验研究

Experimental Study on Linewidth Requirement for Coherent Beam Combination of Fiber Amplifiers in MOPA Configuration

主振荡功率放大器(MOPA)结构光纤激光相干合成通常被认为需要种子源保持单频输出,而由此引入的非线性效应限制了单链路光纤激光的输出功率。采用宽谱种子源和多波长种子源是抑制非线性效应的有效方式。利用随机并行梯度下降法对三路宽谱光纤放大器和三路多波长光纤放大器相干合成进行了实验研究,取得了理想的相干合成效果。实验结果表明,谱线宽度不是制约MOPA结构相干合成的因素,宽谱放大器和多波长放大器的使用有望使MOPA结构光纤激光相干合成系统获得更高功率的输出。

Single-frequency radiation is often considered to be indispensable for coherent beam Combination（CBC） of fiber amplifiers in master oscillator power amplifier（MOPA） configuration.Nevertheless,the single-frequency radiation limits the output power of each single fiber gain due to low stimulated Brillouin scattering（SBS） threshold.Wide linewidth and multi-wavelength radiations are two effective approaches to mitigate SBS effects in fiber amplifiers.Coherent beam combination of three wide-linewidth fiber amplifiers and three multi-wavelength fiber amplifiers are both experimentally demonstrated using stochastic parallel gradient descents（SPGD） algorithm.The experimental results show that single radiation is not indispensable for CBC in MOPA configuration,the application of wide-linewidth and multi-wavelength amplifiers present the potential in achieving a much higher output power in MOPA configuration.