AGSe (AgGaSe2) crystals have band edges at 0.73 and 18 µm. Its useful transmission range (0.9–18 µm) and wide phase matching capability provide excellent potential for OPO applications when pumped by a variety of different lasers. Tuning within 2.5–12 µm has been obtained when pumping by Ho:YLF laser at 2.05 µm; as well as non-critical phase matching (NCPM) operation within 1.9–5.5 µm when pumping at 1.4–1.55 µm. AgGaSe2 (AgGaSe2) has been demonstrated to be an efficient frequency doubling crystal for infrared CO2 lasers radiation.