Ultrabroad tunable (4.5-15 µm) high-energy, high-power picosecond optical parametric oscillator in BGSe crystal

We demonstrate the first, to the best of our knowledge, ultrabroad tunable (4.5-15 μm) mid-infrared (MIR) synchronously pumped optical parametric oscillator (SPOPO) based on BaGa₄Se₇ (BGSe) crystal. Pumped by a burst-mode picosecond 1.064 μm MOPA with 10 sub-pulses, the SPOPO achieves continuous tuning from 4.5 to 15 μm. The average output power exceeds 100 mW over 5.5-11 μm, reaching a maximum of 213.9 mW at 5.7 μm, corresponding to a burst energy of 107 μJ and an average single pulse energy of 13.4 μJ. The quantum efficiency surpasses 20% over 5.2-12 μm and peaks at 34.5% at 7.8 μm. This represents the widest tuning range and the first >100 mW average power in the >8 μm region for an MIR SPOPO. These results highlight the potential of few-pulse burst-mode-pumped SPOPOs for generating widely tunable, high-energy, high-power ultrashort pulses, offering an excellent ultrafast source for MIR applications.