Kerr-lens modelocked Cr:ZnS oscillator for spectroscopy and microscopy applications

High-brightness mid-infrared sources and frequency combs enable several unique spectroscopy and nanoscopy applications such as nano-FTIR and ulra-broadband electro-optic sampling in the molecular fingerprint region [1] . Kerr-lens modelocked (KLM) Cr:ZnS oscillators operating at a wavelength of 2.4 µm combined with a simple single pass amplifier were proven to be a compact pump source for efficient generation of coherent mid-infrared radiation via intra-pulse difference frequency generation (IDFG) in GaSe [2] . Due to their broadband gain medium these oscillators deliver ultrashort laser pulses with durations typically well below 50 fs and peak powers of several hundred kW [3] . We present a stable KLM Cr:ZnS oscillator operating in the negative dispersion regime, which delivers pulses with a duration of 39 fs and a repetition rate of 70 MHz.