A single-longitudinal-mode, narrow bandwidth fiber laser based on an ultra-high roundness microsphere cavity

Abstract

This paper proposes a single-longitudinal-mode, narrow bandwidth fiber laser with double-ring cavity, using an ultra-high roundness microsphere cavity as the single-longitudinal-mode selector. By improving the heating technology and surface cleaning process, microsphere cavities with high Q factor are obtained. Through optimizing the polarization of incident light and the diameter of tapered fiber, Whispering Gallery Mode (WGM) resonance spectrum with a high coupling efficiency of 99.5%, a 3 dB bandwidth of 1 pm and a side mode-suppression-ratio of 14.5 dB is obtained. The proposed fiber laser produces narrow bandwidth laser spectrum with a 3 dB bandwidth of 0.01nm and a high stability without mode-hopping. The proposed fiber laser is of great significance in optical communication and sensing systems.