Sub-Kilohertz Narrow Linewidth Fiber Laser Based on Nanoparticles Doped Self-Injection Module

Fiber lasers with narrow linewidth are essential light sources for many prospects in advanced scientific fields. In this letter, we proposed a scheme of self-injection locked single-frequency fiber laser based on a hybrid cavity configuration and a novel type of nanoparticles doped fiber. The newly proposed hybrid cavity was applied to achieve mode selection in the case of a long cavity which helped increase output power without sacrificing mode instability and single frequency performance. The nanoparticles doped self-injection module helped achieve a fiber laser with 3dB linewidth compressed from 16 kHz to 497 Hz and side mode suppression ratio of more than 60 dB. Furthermore, the sub-kilohertz fiber laser was amplified to more than 1 W with the polarization extinction ratio of similar to 30 dB. Throughout the work, experimental verification and analysis have been carried out to confirm the single frequency lasing performance, including center wavelength drift and slope efficiency variation. The demonstrated watt-level narrow linewidth fiber laser with low RIN and frequency noise has full potential for practical applications.