100 mW broadband tunable mid-infrared frequency comb based on difference frequency generation

Difference frequency generation is a common method for generating mid-infrared laser frequency combs. In this study, we demonstrated a simple mid-infrared laser frequency comb system based on difference frequency generation. A tunable mid-infrared frequency comb covering the wavelength range of 3-4.7 μm was generated on a PPLN crystal using a near-infrared laser frequency comb based on NPR mode locking, with a resolution of 113 MHz within a spectral bandwidth of 80 nm. The mid-infrared frequency comb can reach a maximum optical power of 103.1 mW near 3.3μm, and the pump energy conversion efficiency is 4.91%. This result is expected to be used in mid-infrared spectroscopy applications such as trace gas measurement and combustion field measurement.