An Efficient Continuous Wave Ho:LSO Laser Double-Pass Pumped by a Linewidth-Narrowed Tm Fiber Laser

We report for the first time an efficient continuous wave Ho:LSO laser double-pass pumped by a Tm fiber laser. We achieve a maximum output power equal to 3.6 W at an absorbed pump power of 10.5 W, which corresponds to an optical-to-optical conversion efficiency of 34.3% and a slope efficiency of 59.3%. The output laser wavelength is centered at 2,105.1 nm with a linewidth of ≈2.2 nm, and the beam quality factors ( {mathrm{M}}_x^2 ) = 1.2 and ( {mathrm{M}}_y^2 ) = 1.1 measured by the 90/10 knife-edge method.