Spectroscopy and SESAM mode-locking of a disordered Yb:Gd₂SrAl₂O₇ crystal

We report on the polarized spectroscopy, continuous-wave laser operation, and mode-locked laser performance of an ytterbium-doped disordered tetragonal rare-earth strontium aluminate crystal, Yb³⁺:Gd₂SrAl₂O₇. In the continuous-wave regime, the diode-pumped Yb:Gd₂SrAl₂O₇ laser generated a maximum output power of 487 mW at 1064 nm (π-polarization), with a slope efficiency of 61%. By employing a commercial SESAM to initiate and stabilize soliton-like pulse formation, the mode-locked Yb:Gd₂SrAl₂O₇ laser generated transform-limited pulses as short as 38 fs at 1065.7 nm, with an average output power of 87 mW at a repetition rate of ∼66.5 MHz. The average output power was further scaled to 131 mW for slightly longer pulse duration of 43 fs, corresponding to a peak power of 40.3 kW and a laser efficiency of 15.5%. To the best of our knowledge, this is the first demonstration of mode-locked laser operation of the Yb:Gd₂SrAl₂O₇ crystal.