Used in the production of specialty glasses, particularly infrared-transmitting materials with high refractive indices, due to its ability to transmit light in the mid-infrared range. Commonly found in chalcogenide glasses for thermal imaging systems, sensors, and fiber optics. Also applied in certain types of semiconductors and photoresistors because of its photoconductive properties. Used in thin-film solar cells, particularly as arsenic trisulfide in light-absorbing layers. Serves as an intermediate in the synthesis of complex materials for materials science research. Historically used in pigments for paints and in pyrotechnics for color enhancement, though such uses have declined due to toxicity concerns. Investigated for use in optoelectronic devices and phase-change memory materials.