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 CdGa₂X4₄(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 View the MathML source|χijk(2)(ω)| and microscopic first hyperpolarizability βijk (ω ) were calculated. The calculated View the MathML source|χ123(2)(ω)| and View the MathML source|χ312(2)(ω)| static values for the dominant components found to be 18.36 pm/V and 22.23 pm/V for CdGa₂S₄ and CdGa₂Se₄. Both values shifted to be 60.12 pm/V and 108.86 pm/V at λ = 1064 nm. The calculated values of β123(ω) is 6.47 × 10−³º esu at static limit and 12.42 × 10−³º esu at λ = 1064 nm for CdGa₂S₄, whereas it is 8.82 × 10−³º esu at static limit and 20.51 × 10−³º esu at λ = 1064 nm for CdGa₂Se₄. The evaluation of second order susceptibilities and first hyperpolarizabilties suggest that CdGa₂X₄ possess huge second harmonic generation.