High-power thulium-doped fiber lasers (TDFLs) operating near 2050 nm are of great interest for applications including atmospheric gas sensing and free-space optical communication owing to the favorable atmospheric transmission and the strong absorption bands of carbon dioxide (CO2). Here, we report an all-fiber high-power TDFL based on a 793 nm-pumped master oscillator power amplifier (MOPA) architecture. The system comprises a custom-built linear-cavity seed laser and two amplification stages. With a maximum pump power of 818 W, the final amplifier delivers 501 W at 2050 nm with a slope efficiency of 51%. Stable operation is confirmed over two hours at full power, with an RMS power fluctuation of only 0.47%. The measured beam quality factors M2 are 1.31 and 1.27 in the horizontal and vertical directions, respectively, indicating near-diffraction-limited performance. The demonstrated system combines high output power, excellent stability, and good beam quality, and thus provides a promising laser source for 2 μm high-performance applications.
Peng et al. (Wed,) studied this question.