3.3 W picosecond LWIR generation via ZnGeP₂ and BaGa₄Se₇ difference frequency generation

We demonstrate a high-power picosecond long-wave infrared (LWIR) source based on type-II difference frequency generation (DFG) in ZnGeP₂ (ZGP) and BaGa₄Se₇ (BGSe), pumped by a 2089.1 nm laser at 10 kHz repetition rate. When seeded by a double-pass optical parametric generator (OPG), the system delivers a record tabletop 1.91 W idler output beyond 10 μm from BGSe DFG under 56 W total pump power. The type-II ZGP DFG stage alone generates 2.84 W beyond 10 μm, while cascading with BGSe boosts the average power to 3.31 W, corresponding to 5.9% optical-to-optical conversion efficiency. The idler spectrum centers at 10.02 μm with 278 nm full-width at half-maximum (FWHM) bandwidth. With measured a 252.5 ps pulse duration, the system achieves 1.31 MW peak power and beam quality M² = 3.64/2.67 in x/y directions. To our knowledge, this represents the highest average power reported from LWIR parametric sources beyond 10 μm.