Compact Ho:YAG Laser at 2.1- $\mu$ m Mode Locked by Re-Absorption

The compact self-mode-locking Ho:YAG laser pumped by the Tm-doped fiber laser was obtained based on the re-absorption effect. At the incident pump power of 26.9 and 35.4 W, the pulse widths of 431.3 and 471.6 ps were achieved, respectively, and the corresponding average powers reached 3.3 and 4.27 W leading to the optical-to-optical efficiencies of 12.26% and 12.06%, respectively. The center wavelength was 2128.36 nm and the repetition rate was 656.6 MHz. To the best of our knowledge, this is the first report on the self-mode-locking Ho:YAG laser applying the re-absorption effect as the modulating mechanisms. The numerical analysis on the photon density and population inversion density considering the re-absorption loss could demonstrate the contribution of the re-absorption effect in the pulse generation. The compact configuration with the high repetition rate and the room-temperature operation could determine the promising future of self-mode-locking Ho:YAG in application areas.