High-power sub-two-cycle mid-infrared pulses at 100 MHz repetition rate

Powerful coherent light with a spectrum spanning the mid-infrared (MIR) spectral range is crucial for a number of applications in natural as well as life sciences, but so far has only been available from large-scale synchrotron sources(1). Here we present a compact apparatus that generates pulses with a sub-two-cycle duration and with an average power of 0.1 W and a spectral coverage of 6.8-16.4 mu m (at -30 dB). The demonstrated source combines, for the first time in this spectral region, a high power, a high repetition rate and phase coherence. The MIR pulses emerge via difference-frequency generation (DFG) driven by the nonlinearly compressed pulses of a Kerr-lens mode-locked ytterbium-doped yttrium-aluminium-garnet (Yb:YAG) thin-disc oscillator. The resultant 100 MHz MIR pulse train is hundreds to thousands of times more powerful than state-of-the-art frequency combs that emit in this range(2-4), and offers a high dynamic range for spectroscopy in the molecular fingerprint region(4-7) and an ideal prerequisite for hyperspectral imaging(8) as well as for the time-domain coherent control of vibrational dynamics(9-11).