Zinc germanium phosphide (ZnGeP2) is an excellent mid-IR nonlinear crystal with many outstanding fundamental properties. ZnGeP2 (ZGP) crystal has large nonlinear susceptibility (d36~75 pm/V), which is approximately 160 times that of KDP. ZGP exhibits good optical transparency over the 0.74–12μm wavelength region and relatively high laser damage threshold, and is therefore well suited for producing tunable laser output in the near infrared. ZGP is a very promising material for applications such as SHG, SFG, OPO, and OPG/OPA in the mid-infrared region.