Zirconium pentatelluride as saturable absorber for 2 mu m ultrafast solid-state laser

A high-quality 2 mu m ultrafast laser is successfully developed using a zirconium pentatelluride saturable absorber mirror (ZrTe5-SAM) composed of a layered structure of ZrTe5. Continuous wave mode-locked (CWML) operation has been demonstrated in the fabricated laser with Tm:YAG ceramic as the laser gain medium. Ultrafast pulses as short as 4.8 ps are obtained with a maximum average output power of 767 mW and a repetition frequency of 56 MHz, at a central wavelength of 2014 nm. To the best of our knowledge, this is the highest average output power achieved so far, for a passively mode-locked laser at 2 mu m using a two-dimensional (2D) saturable absorber (SA). This study opens new doors for the development of high power 2 mu m ultrafast lasers.