Growth and characterization of the chalcopyrite LiGaTe2: A highly non-linear birefringent optical crystal for the mid-infrared

LiGaTe2 crystals have been grown by the Bridgman–Stockbarger technique. The clear transparency range of LiGaTe2 extends from 2.5 to 12 μm and its band-gap at room temperature is at 2.41 eV (515 nm). LiGaTe2 is a positive uniaxial crystal which possesses sufficient birefringence for phase-matching. Its non-linear coefficient d36 estimated by phase-matched second harmonic generation is 43 pm/V ± 10% at 4.5 μm. The properties of LiGaTe2 are compared to those of other mid-IR chalcopyrite non-linear optical crystals with special emphasis on the frequency doubling potential for CO2 lasers operating at 10.6 μm.