Study of a multi-ring cavity based single-frequency fiber laser and associated thermal effects

Abstract

• A concise criterion for length selection is proposed for multi-ring fiber cavities. • Influence of thermal tampering on modal selection is analyzed and verified. • Stable single-frequency Yb-doped fiber lasers of multi-ring cavities are achieved. In this paper we present a detailed study of compound ring resonator based fiber lasers for single-frequency (SF) generation and associated thermal effects. A concise criterion to select a single longitudinal mode (SLM) by the multi-ring cavity (MRC) scheme is proposed and confirmed with experiments on fiber lasers with zero, one, and two sub-ring cavities. The results demonstrate the necessity of using at least two sub-rings of tight length differential to ensure stable SF laser emission by the MRC scheme. Subsequent studies of temperature variation upon the two sub-rings reveal that the robustness of SF emission status can be further secured by a controlled thermal tampering process. Stable SF emission, centered at 1064.2 nm with a 3-dB linewidth of <10 kHz, are thus achieved by Yb-doped all-fiber lasers with the MRC scheme.