High energy and tunable mid-infrared source based on BaGa4Se7 crystal by single-pass difference-frequency generation

A high-energy and tunable mid-infrared source based on BaGa4Se7 crystal was demonstrated by single-pass difference-frequency generation (DFG). Orthogonally polarized wave at 1064 nm (λ1) and tunable idler wave (λ2) generated by KTP-OPO, which could be tuned in the wavelength range of 1360-1600 nm, were used as the DFG dual-wavelength pump. The pump parameters including total pump energy and energy ratio were studied. Maximum pulse energy of 5.72 mJ at 3.58 μm was obtained at the dual-wavelength pump energy of 58.4 mJ/pulse. The wavelength tuning range was 3.36-4.27 μm with a flat tunability. Moreover, a saturation phenomenon of DFG output was observed and experimentally inferred to be related to the input energy of λ2 in the BaGa4Se7 crystal.