Kerr-lens mode-locked 49-fs Tm 3+ :YScO 3 single-crystal laser at 2.1 µm.

We report on a continuous wave (CW) and Kerr-lens mode-locked (KLM) Tm:YScO single-crystal laser centered at 2.1 µm. Efficient CW laser operation with a maximum slope efficiency of 51% was achieved under in-band pumping by an Er:Yb fiber master oscillator power amplifier (MOPA). In KLM operation, pulses as short as 49 fs corresponding to seven optical cycles were achieved at a repetition rate of 96.7 MHz with an average output power of 126 mW. Such short pulse durations are enabled by the inhomogeneously broadened emission spectrum of Tm:YScO extending to above 2200 nm.