为获得可应用于光载微波雷达系统的高功率双频激光源, 用1 064 nm窄线宽Nd∶YAG单块非平面环形腔激光器作为单频种子源, 其输出分为两路, 一路直接耦合入光纤, 另一路经声光移频, 与未移频的光束合束后获得中心频差为150 MHz、功率为20 mW的双频激光.利用以半导体激光泵浦和掺Yb3+石英光纤为增益介质的3级主振荡功率放大系统对双频固体激光器输出的双频激光进行放大, 获得50.3 W的双频放大输出, 光束质量因子为1.30, 第三级主放大斜效率为74%.双频成分的幅度比、频差在放大过程中得到保持, 拍频调制深度及信噪比等特性也未有恶化.双频光纤功率放大器在频差稳定和高功率输出等方面均有良好的表现.

To obtain the high power dual-frequency laser source for lidar-radar system, a narrow-linewidth Nd∶YAG monolithic nonplanar ring-oscillator laser with central wavelength of 1 064 nm was uesd as a single-frequency seed laser. The output was split into two parts, one was transmitted in optical fiber and the other was frequency shifted by an acoustooptic modulator. The combined beam had power of 20mW and contained two frequency components with frequency separation of 150 MHz. A three-stage master oscillator power amplifier using diode laser pumped and Yb3+-doped quartz fiber as gain medium was proposed to boom the output power of dual-frequency laser. The maximum amplified power was 50.3 W, beam quality factor was 1.30 and the slope efficiency of the third-stage main amplifier was 74%. The amplitude ratio and frequency separation of the dual-frequency components were maintained in the amplification process. The modulation depth and signal-noise ratio of the beat signal had not deteriorated. Dual-frequency laser fiber power amplifier provides robust performance of both the stable beat frequency and the relative high output power.