Sub-6 optical-cycle Kerr-lens mode-locked Tm:Lu₂O₃ and Tm:Sc₂O₃ combined gain media laser at 2.1 μm

We present a combined gain media Kerr-lens mode-locked laser based on a Tm:Lu₂O₃ ceramic and a Tm:Sc₂O₃ single crystal. Pulses as short as 41 fs, corresponding to less than 6 optical cycles, were obtained with an average output power of 42 mW at a wavelength of 2.1 μm and a repetition rate of 93.3 MHz. Furthermore, a maximum average power of 316 mW with a pulse duration of 73 fs was achieved.