Abstract

Mode-locked laser operation in the two-micrometer range is a very interesting subject and has important potential applications in a number of areas, including optical frequency combs and high order harmonics generation. Tm-doped sesquioxides (Tm³⁺:Re₂O₃, Re=Sc, Lu or Y) are one of the most promising candidates as the gain media for a mode-locked laser in the two micron range. The shortest pulse duration of Tm-doped solid-state laser reported nowadays is 148 fs from a Tm³⁺:LuScO₃ crystal [1]. For mode locked lasers, a Ti³⁺:Al₂O₃ pump laser at the wavelength of ~800 nm was often used, because of its high beam quality and the characteristic two-for-one pump process of the Tm-ion. However, Ti³⁺:Al₂O₃ laser pumping limits the power scalability and the total conversion efficiency of the mode-locked laser. In addition, Tm-doped sesquioxides suffer low absorption cross sections around the pump wavelength of 800 nm (Tm³⁺:Sc₂O₃~0.45×10⁻²⁰) which requires thick crystals and also restricts the design of the laser cavity. Tm³⁺:Sc₂O₃ has a narrow absorption peak at 1611.5 nm with an absorption cross-section of ~0.8 ·10^-20 cm² which is almost twice as high compared to ~800 nm. In this paper, we have demonstrated a Tm³⁺:Sc₂O₃ laser in-band pumped by a 1611.5 nm Er-fiber laser which could provide better power scalability and better flexibility of the laser cavity.

© 2015 IEEE