Abstract

Efficient high-power lasers emitting at a wavelength of around 2.12 µm are of increasing interest for applications taking advantage of a broad atmospheric transmission window. Typically, Ho³⁺-doped fiber lasers (HDFL) are used to address this wavelength region due to much higher emission cross sections compared to their 2 µm equivalent Thulium lasers [1,2]. Recently, Tm³⁺:Ho³⁺-codoped fiber lasers were demonstrated with a slope efficiency as high as 56 % [3] and output powers up to 260 W [4], thus making them a sound substitute to HDFLs for operation above 2.1 µm. The free-space setup shown in [4] is now transferred to a more integrated and rugged all-fiber version. To the best of our knowledge, we show the first realization of a Tm³⁺:Ho³⁺-codoped all-fiber laser emitting at 2120 nm with a slope efficiency close to 50 %.

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