Sub-50-fs SESAM mode-locked Tm,Ho:Ca(Gd,Lu)AlO4 laser

Thulium (Tm 3+ )- and holmium (Ho 3+ )- codoped tetragonal calcium rare-earth aluminates CaLnAlO 4 where Ln stands for Gd and Y (denoted as CALGO and CALYO, respectively) feature the advantages of broad and smooth gain spectra due to the significant inhomogeneous broadening in the K 2 NiF 4 -type disordered structure, good thermal and thermo-optical properties of the host crystals as well as polarized emission due to the natural birefringence, which make them attractive for the development of tunable and sub-100 fs solid-state lasers in the 2-μm spectral region [1] - [4] . While the isostructural host CaLuAlO 4 was never been successfully grown, mixed Tm,Ho:Ca(Gd 1-x Lu x )AlO 4 (shortly Tm,Ho:CALGLO) crystals with a partial substitution of Gd 3+ by Lu 3+ are expected to provide additional broadening of the spectral bands due to the compositional disorder. Here, we report on a semiconductor saturable-absorber mirror (SESAM) mode-locked (ML) Tm,Ho:CALGLO crystalline laser generating pulses as short as 47 fs with an average power of 121 mW at 2033 nm.