Novel ternary semiconductor CdLa2X4 (X=S or Se) single crystal with efficient second harmonic generation in the visible spectral range

Comprehensive ab-inito calculations are performed to investigate the suitability of the non-centro-symmetric CdLa2S4 and CdLa2Se4 for using as nonlinear optical crystals in visible spectral range. The calculations reveal the direct band gap nature of both compounds with large absorption coefficient (104 cm−1). The absorption edges of CdLa2S4 and CdLa2Se4 occur at λ = 579.3 nm and λ = 670.1 nm, and the optical band gaps are estimated to be 2.14 eV and 1.85 eV for CdLa2S4 and CdLa2Se4, respectively. CdLa2S4 exhibits SHG of about two times of the well-known KH2PO4 (KDP) single crystals which exhibits a nonlinear coefficient of 0.39 p.m./V. Whereas CdLa2Se4 exhibits SHG very close to the experimental value of that for the well-known KTiOPO4 (KTP) which exhibits a nonlinear coefficient of about 14.6 ± 1.0.