Dispersion of the second harmonic generation from CdGa2X4 (X = S, Se) defect chalcopyrite: DFT calculations

Abstract

All electron full potential linear augmented plane wave method was used for calculating the nonlinear optical susceptibilities of CdGa2X4 (X=S,Se) within the framework of density functional theory. The exchange correlation potential was solved by recently developed modified Becke and Johnson (mBJ) approximation. The crystal structure of CdGa2S4 and CdGa2Se4 reveals a large uniaxial dielectric anisotropy ensuing the birefringence of −0.036 and −0.066 which make it suitable for second harmonic generation. The second order susceptibility |χijk(2)(ω)| and microscopic first hyperpolarizability βijk(ω) were calculated. The calculated |χ123(2)(ω)| and |χ312(2)(ω)| static values for the dominant components found to be 18.36pm/V and 22.23pm/V for CdGa2S4 and CdGa2Se4. Both values shifted to be 60.12pm/V and 108.86pm/V at λ=1064nm. The calculated values of β123(ω) is 6.47×10−30esu at static limit and 12.42×10−30esu at λ=1064nm for CdGa2S4, whereas it is 8.82×10−30esu at static limit and 20.51×10−30esu at λ=1064nm for CdGa2Se4. The evaluation of second order susceptibilities and first hyperpolarizabilties suggest that CdGa2X4 possess huge second harmonic generation.