Zinc selenide (ZnSe) is a binary compound semiconductor with a cubic zinc blende structure. This material is transparent in the visible and near-infrared regions of the electromagnetic spectrum, with a wide direct bandgap of approximately 2.7 eV. Due to its transparency and high refractive index, ZnSe has become a popular choice for high-power infrared laser systems, especially CO2 lasers, where ZnSe optics are used as output couplers and beam expanders. ZnSe can also be doped with various elements, most notably with chromium (Cr:ZnSe), to produce mid-infrared solid-state lasers. In addition, ZnSe is utilized in the fabrication of light-emitting diodes, photodetectors, and solar cells.