mP20 P21/c 14Arsenic triselenide (As2Se3) is an inorganic chemical compound, a selenide of arsenic. Arsenic triselenide (As2Se3) is an inorganic chemical compound, a selenide of arsenic. Amorphous arsenic triselenide is used as a chalcogenide glass for infrared optics, as it transmits light with wavelengths between 870 nm and 17.2 µm . Arsenic triselenide is covalently bonded. Even so, the arsenic has a formal oxidation state of +3. Thin film selenide glasses have emerged as an important material for integrated photonics due to its high refractive index, mid-IR transparency and high non-linear optical indices. High-quality As2Se3 glass films can be deposited from spin coating method from ethylenediamine solutions.