Fig. 1. Experimental setup

Fig. 2. Type-II PM angles and effective NLO coefficient (d_eff) of LISe-OPA pumped using 1064 nm laser

Fig. 3. Calculated idler energy at 8.1 μm as a function of (a) pump energy for LISe crystals of different lengths; (b) crystal length under a specified pump energy

Fig. 4. (a) Transmission spectrum for 4-mm-thick uncoated LISe crystal (lower left inset: photograph of sample); (b) measured transmission of LISe based on 1064 nm pump laser

Fig. 5. Idler energy at 8.1 μm vs. pump energy for LISe-OPA at normal incidence. Lower right inset: idler energy vs. seed energy at fixed pump energy of ∼5 mJ

Fig. 6. Wavelength dependence of idler energy from 6.5 to 12 µm for LISe-OPA at pump energy of 9.4 mJ (lower left inset: spectrum of signal laser at 1224.9 nm)

Fig. 7. Normalized conversion efficiency of LISe-OPA at 8.1 μm as a function of (a) angle φ and (b) signal wavelength λ_s