Upconversion-pumped femtosecond thulium laser at 2309 nm mode-locked by a GaSb-based SESAM
Aleksey Tyazhev, Jı Eun Bae, Marco Gaulke, Pavel Loiko, Jonas Heidrich, M. Golling, Saïd Idlahcen, Lauren Guillemot, Thomas Godin, Patrice Camy, U. Keller, Ammar Hideur
Abstract
We report on a femtosecond thulium laser operating on the 3 H 4 → 3 H 5 transition with upconversion pumping around 1 µm and passively mode-locked by a GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM). This laser employs a 6 at.% Tm:LiYF 4 laser crystal and a polarization maintaining Yb-fiber master oscillator power amplifier at 1043 nm as a pump source addressing the 3 F 4 → 3 F 2,3 excited-state absorption transition of Tm 3+ ions. In the continuous-wave regime, the Tm-laser generates 616 mW at ∼2313 nm with a slope efficiency of 10.0% (vs. the incident pump power) and a linear polarization (π). By implementing a type-I SESAM with a single ternary strained In 0.33 Ga 0.67 Sb quantum well embedded in GaSb for sustaining and stabilizing the soliton pulse shaping, the self-starting mode-locked Tm-laser generated pulses as short as 870 fs at a central wavelength of 2309.4 nm corresponding to an average output power of 208 mW at a pulse repetition rate of 105.08 MHz and excellent mode-locking stability. The output power was scaled to 450 mW at the expense of a longer pulse duration of 1.93 ps. The nonlinear parameters of the SESAM are also reported.