Broadband LWIR generation based on a Yb-doped fiber laser

Laser spectroscopy in the longwave mid-infrared (LWIR) region reveals the structures and properties of various biochemical substances. Here, we demonstrate a broadband LWIR laser covering 5.7–11.0 μm with 13 mW average power and 108 MHz repetition rate based on difference frequency generation (DFG) in a zinc germanium phosphide (ZGP) crystal. The laser can also be widely tuned over 4.6–11.0 μm with a maximum average power of 40 mW. The pump and signal pulses of DFG are generated from a broadband optical parametric oscillator (OPO) system pumped by a Yb-doped fiber laser. Absorption spectroscopy of an organic compound was demonstrated by the LWIR source. Furthermore, combining additional complex phase locking, it has the potential to achieve dual comb spectroscopy (DCS) for higher measurement speed and resolution. The adjustment-free LWIR lasers with instantaneous broadband spectra reduce system complexity and alignment difficulty, and they are desirable for sensitive parallel molecular spectroscopy and biological macromolecule detection.