ZGP – Zinc germanium phosphide

ZnGeP₂ (zinc germanium phosphide) is a nonlinear optical crystal distinguished by its exceptionally high nonlinear coefficient, wide transparency range in the mid-infrared region (roughly 2–12 μm), and relatively good thermal conductivity, which together make it one of the most efficient materials for frequency conversion processes; it is widely used in optical parametric oscillators, amplifiers, and difference-frequency generation systems to produce tunable mid-IR laser radiation, although its practical use requires careful handling due to residual absorption and sensitivity to high optical intensities.