High-efficiency, 100-μJ-level mid-infrared ultrashort pulses from a burst-mode, few-pulse OPO design

We demonstrated the efficient generation of high-energy, mid-infrared, ultrafast pulses by using a burst-mode, few-pulse, synchronously pumped optical parametric oscillator (BF-SPOPO). The overall efficiency was 2-5 times higher than that of previous OPA and DFG schemes and an improvement of approximately two orders of magnitude compared to the current pulse energy of SPOPO. These improvements were due to the few-pulse burst-mode design, which integrated high-gain characteristics with multi-pass circulating amplification, and achieved high conversion efficiency, based on the BaGa₄Se₇ crystal. In a low-energy pump configuration (1064 nm picosecond pulses), the maximum estimated single-pulse energy at 6.5 μm reaches 34.2 μJ; Across the 5.6-7 μm range, the overall quantum efficiency approaches 40%, with a tuning span of 5-9 μm and a maximum average power of 215.1 mW. In a high-energy configuration, the idler burst energy at 6.5 μm attains 325.8 μJ, corresponding to an average sub-pulse energy of 108.6 μJ and a peak power of 11.3 MW. This research overcame the inherent difficulty of generating high-energy ultrashort pulses in conventional SPOPOs, demonstrating the potential of BF-SPOPO as a general strategy for efficient, high-energy, high-average-power picosecond or femtosecond pulse generation.