Ag3Ga3SiSe8: a new infrared nonlinear optical material with a chalcopyrite structure

Abstract

An infrared (IR) nonlinear optical (NLO) material, Ag₃Ga₃SiSe₈, has been synthesized for the first time. It crystallizes in the tetragonal chalcopyrite AgGaSe₂ structure type and the substitution of Ga³⁺ with Si⁴⁺ generates an equal amount of vacancies at the Ag⁺ position. Ag₃Ga₃SiSe₈ is a congruent melting compound with a melting temperature of 784 °C. The second-harmonic generation (SHG) effect of Ag₃Ga₃SiSe₈ is similar to that of AgGaSe₂, as confirmed by the first-principles studies. Moreover, the diffuse reflectance spectra reveal that the energy band gap of Ag₃Ga₃SiSe is 2.30 eV, 0.44 eV larger compared with AgGaSe₂ (1.86 eV). The birefringence of Ag₃Ga₃SiSe₈ is predicted to be above 0.1 at the wavelength of 1 μm, significantly larger than that of AgGaSe₂ (Δn ~ 0.02). Our results indicate that Ag₃Ga₃SiSe₈ may possess improved optical properties compared with AgGaSe₂ and has a promising application as a good IR NLO material.