LiGaGe₂S₆: A Chalcogenide with Good Infrared Nonlinear Optical Performance and Low Melting Point

In this work, we design and synthesize a new chalcogenide LiGaGe₂S₆ on the basis of known infrared (IR) material LiGaS₂ by partially substituting Ga with Ge. This compound possesses very strong nonlinear (NLO) response (2.5 × LiGaS₂) and large band gap (3.52 eV), manifesting a better balance between band gap and NLO response compared with that for LiGaS₂. Moreover, LiGaGe₂S₆ exhibits a much lower melting point (663 °C) than that of LiGaS₂ (1050 °C). This would result in the much smaller vapor pressure of sulfur in the fused quartz vessels used for the crystal growth, and thus, it should be greatly beneficial to obtain the large stoichiometric LiGaGe₂S₆ single crystal. Our studies demonstrate that LiGaGe₂S₆ is a good candidate material for IR NLO applications