High-gain fluoro-sulfo-phosphate-based active fiber for compact low-threshold kilohertz-linewidth single-frequency fiber laser

Abstract

Single-frequency fiber lasers (SFFLs) are of pivotal importance across optical communication, scientific research and national defense due to their excellent beam quality, long coherent length and low noise. However, the development of high-gain rare-earth-doped glass fibers, which are the key medium used in the SFFLs, remains a critical scientific challenge. To address this issue, we design and fabricate a single-mode fluoro-sulfo-phosphate-based Er3+/Yb3+-codoped glass fiber (denoted as FSP-EYDF). The gain properties and laser performance of the FSP-EYDF have been investigated comprehensively. The results show that the small signal gain coefficient of the home-made FSP-EYDF can reach 4.7 dB/cm at 1535 nm, which is three times higher than that of the silica glass fiber. A short piece of FSP-EYDF with a length of only 1.6 cm has been utilized as a gain medium to support an SFFL operating at 1534.4 nm, which has a threshold of ∼18 mW and a linewidth of 3.15 kHz. This study indicates that high-gain FSP fibers are promising candidates for compact low-threshold narrow-linewidth SFFLs.