1.5-W diode-pumped femtosecond Cr:ZnS amplifier

Carrier-envelope-phase stable, multi-octave-spanning light sources enable novel types of spectroscopy techniques with unprecedented high sensitivity and dynamic range [1] , [2] . They are thus highly sought after, especially in the mid-infrared molecular finger-print region. Cr:ZnS lasers — capable of directly emitting sub-30 fs pulses at a central wavelength around 2.4 µm and at multi-Watt-level of average power [3] , [4] — are the ideal front-end for generating such spectral coverage [5] . These lasers have predominantly been pumped using rare-earth-doped fiber lasers, which often exhibit intensity noise in the kHz range arising from relaxation oscillations. The subsequent transfer of such noise to the Cr:ZnS output in turn affects the signal-to-noise ratio for downstream spectroscopy applications. This can be alleviated by pumping the Cr:ZnS lasers with the direct output of diode lasers, which can also be more cost effective. To this end, we have recently demonstrated a directly diode-pumped femtosecond Cr:ZnS oscillator [6] . To further enhance the available power and widen its possible applications, we report here the first demonstration of a directly diode-pumped Cr:ZnS amplifier, to the best of our knowledge.