Narrow linewidth self-injection locked fiber laser based on a crystalline resonator in add-drop configuration

Strong and narrow spectral feedback plays a key role in self-injection locking (SIL) single-frequency lasers, especially in the stabilization of single longitudinal mode (SLM) operation of a multi-mode laser. Here, we report on a narrow linewidth SH, fiber laser that adopts a fiber add-drop configuration composing of two tapered fibers and a high-Q MgF2 crystalline whispering-gallery-mode resonator. The feedback from the drop port could be controlled and optimized for stable SLM lasing of multi-mode fiber lasers. A stable single-frequency fiber laser with white frequency noise as low as similar to 0.4 Hz(2)/Hz, corresponding to an instantaneous linewidth of similar to 1.26 Hz, is demonstrated. Compact, control-lable, and all-fiber configuration in this work to achieve an ultra-narrow linewidth laser will attract interest in many applications. (C) 2022 Optica Publishing Group

Automated summary

In this study, we present a narrow linewidth SH fiber laser that utilizes two tapered fibers and a high-Q MgF2 crystalline whispering-gallery-mode resonator. By controlling the feedback from the drop port, stable single longitudinal mode (SLM) operation of multi-mode fiber lasers is achieved. The experimental results demonstrate a stable single-frequency fiber laser with ultra-low white frequency noise and instantaneous linewidth. This compact, controllable, and all-fiber configuration for ultra-narrow linewidth laser is of great significance in various applications.