Birefringence, linear and nonlinear second-order optical susceptibilities of a noncentrosymmetric chalcopyrite compound HgGa 2S 4

Abstract

We present the results of the ab initio theoretical study of the linear and nonlinear optical susceptibilities for the HgGa 2S 4 single crystals using the all electron full potential-linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. We have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure and optical susceptibilities calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap. We present calculations of the frequency-dependent complex dielectric function ε( ω) and its zero-frequency limit ε 1(0). The optical properties are analyzed, and the origin of some of the spectral peaks is discussed in terms of the calculated electronic band structure. The edge of optical absorption for ε 2 xx ( ω ) and ε 2 zz ( ω ) is located at 2.8 eV. The linear optical properties shows a large negative uniaxial anisotropy and birefringence which favors large second-order susceptibility χ ijk ( 2 ) ( ω ) . The imaginary and real parts of the second-order SHG susceptibility were evaluated. Our calculation show that χ 213 ( 2 ) ( ω ) is the dominant component which shows the largest total Re χ ijk ( 2 ) ( 0 ) valve 5.4 pm/V.