High-Power-Seed Femtosecond Long-Wave Infrared Difference Frequency Generators

Long-wave infrared (LWIR) femtosecond optical pulses with high repetition rates (typically > 10 MHz) are essential for constructing LWIR optical frequency combs and have attracted great interest in many applications of infrared spectroscopy [1], [2]. A common approach for generating LWIR femtosecond pulses is using frequency- conversion devices, e.g., difference frequency generators (DFGs). Recent theoretical analysis shows that the power of DFG systems can be scaled by enhancing the pulse energy of the incident signal wave to the same level as the pump [3]. However, there is still a lack of a universal experimental scheme for achieving high-repetition-rate DFG with seed and pump pulses having the same power. Here, we report a high-power-seed femtosecond LWIR DFG system based on two femtosecond OPOs for efficiently obtaining widely tunable LWIR pulses.