Opt Lett. 2018 Nov 15;43(22):5535-5538. doi: 10.1364/OL.43.005535.
This Letter describes an experimental realization of a double-pass amplifier using rod-type fiber. In this device, the gain reaches 26 dB amplifying a 300 mW, 20 ps, 20 MHz seed up to 120 W, with an optical-to-optical efficiency of 50% and excellent beam quality. In addition, by design the output of the amplifier has a polarization extinction ratio of 33 dB. Besides these good performances, we report a marginal degradation of mode quality and degree of polarization followed by the so-called transverse mode instability which occurs at 120 W signal power. The first degradation is static, and by analyzing its two polarizations, we conclude it is caused by a coupling between modes due to the formation of a static thermal long-period grating, which in turn initiates the dynamic instability.
这封信件描述了一种使用棒型光纤的双通放大器的实验实现。在这个设备中，增益达到 26dB，将 300mW、20ps、20MHz 的种子放大到 120W，光光效率为 50%，光束质量优良。此外，通过设计，放大器的输出具有 33dB 的偏振消光比。除了这些良好的性能，我们报告了模式质量和偏振度的轻微劣化，随后是所谓的横向模式不稳定性，这种不稳定性发生在 120W 信号功率下。第一次劣化是静态的，通过分析其两个偏振方向，我们得出结论，这是由于模式之间的耦合引起的，这是由于形成静态热长周期光栅所致，这反过来又引发了动态不稳定性。
