Frequency divide-and-conquer approach to creating ultrabroadband frequency combs in the mid-IR-THz region

We present a new technique for generating frequency combs in the mid-IR with potential extension to the THz spectral range, based on division of the frequency of a pump laser in a subharmonic optical parametric oscillator (OPO). Almost two-octaves-wide, 3-10 μm (30-90 THz) frequency comb with high spectral purity was demonstrated and applied to dual-comb coherent molecular spectroscopy.