Compact Hundred-mW $2~\mu \text{m}$ Single-Frequency Thulium-Doped Silica Fiber Laser

Abstract

The output characteristics of a 2- $\mu \text{m}$ all-silica-fiber single-frequency distributed Bragg reflector (DBR) laser in-band pumped by a 1570-nm fiber laser were investigated in this letter. More than 50-mW laser power was obtained in this all-silica-fiber laser system with the linewidth of ~ 36 kHz. Low relative intensity noise was achieved in the experiment due to the superior noise properties of 1570-nm fiber laser as pump source, especially at the relaxation oscillation frequency, where the noise intensity is measured to be as low as −112 dB/Hz. With another piece of Tm3+-doped fiber spliced directly to the DBR laser to effectively exploit the pump power, a compact hundred-mW single-frequency fiber laser at 1920 nm was obtained without performance degradation. The compact hundred-mW all-silica-fiber single-frequency laser system we demonstrated here can be a competitive candidate to promote the popularization of $2~\mu \text{m}$ single-frequency fiber laser for the applications such as free-space optical communication and LIDAR.