Kerr-lens mode-locked femtosecond polycrystalline Cr2+:ZnS and Cr2+:ZnSe lasers.

We report the first Kerr-lens mode-locked polycrystalline Cr(2+):ZnS and Cr(2+):ZnSe lasers, with pulse duration of 125 fs at a pulse repetition rate of 160 MHz, emitting around 2.3 - 2.4 µm. The mode-locked lasers were pumped by a radiation of 1550 nm Er-fiber amplifier seeded by semiconductor laser. The long-term stable Kerr-lens mode-locked laser operation with the output power of 30 mW (Cr(2+):ZnS) and 60 mW (Cr(2+):ZnSe) was obtained. We also demonstrate amplification of the fs laser pulse train in a cw pumped single-pass polycrystalline Cr(2+):ZnS laser amplifier.