Comparison of mid-IR nonlinear crystals with integral figure of merit

Here, we estimate the conversion efficiency of several mid-IR crystals using a simple integral criterion that was verified on experimental data and gave good agreement. Calculations show that the ZnGeP
₂
crystal is the most efficient crystal in the wavelength range of 4.1-7.7 μm for narrowband frequency conversion (5.4-6.5 μm for broadband frequency conversion). For longer wavelengths, CSP and HGS crystals are the most efficient.