Ultrashort-pulsed Kerr-lens modelocked Cr:ZnSe laser

In this work, we report the first truly Kerr-lens modelocked regime of operation of Cr:ZnSe laser. The laser has been assembled according to a classic X-cavity with all non-dispersive mirrors. The dispersion compensation has been achieved by a 6-mm YAG plate. The laser has been operating in open air, at relative humidity of 32%. With an overall cavity round-trip length of 150 cm, the water vapour in the air resulted in strong absorption lines above 2.45 mum. As a result of this absorption, the laser has operated in two distinct regimes: high-power soliton regime with -300 mW of output power and 100 fs duration, and chirped pulse regime with 170 mW of output power and ~1 ps pulse duration. The spectrum in the second regime has been strongly shifted to the blue side, where the water apsorption is negligible, but the intracavity dispersion was nearly zero. The mode-locked operation in the chirped regime regime was long-term stable and self-starting, while the soliton regime could hold only for minutes.