AUTHOR=Shi Chaodu , Deng Xun , Fu Shijie , Sheng Quan , Jiang Peiheng , Shi Zheng , Li Yanyan , Shi Wei , Yao Jianquan TITLE=700 W single-frequency all-fiber amplifier at 1064 nm with kHz-level spectral linewidth JOURNAL=Frontiers in Physics VOLUME=10 YEAR=2022 URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2022.982900 DOI=10.3389/fphy.2022.982900 ISSN=2296-424X ABSTRACT=

In this work, a single-frequency fiber amplifier with output power of 703 W was demonstrated at 1,064.4 nm in an all-fiber configuration. Cascaded Yb3+-doped fiber structure with different dopant concentration and hybrid 915/976 nm pump scheme were employed in power scaling stage to improve the gain saturation for higher transverse mode instability threshold. An overall optical efficiency of 67.5% was achieved at the maximum output power and the M2 was measured to be ∼1.4. A spectral linewidth of 2 kHz was obtained from the 703-W single-frequency laser. To the best of our knowledge, this is the first time that a single-frequency all-fiber amplifier with kHz-level spectral linewidth is achieved at such high output power.