Ab initio study of the linear and nonlinear optical properties of hexagonal CdSe

We present an ab initio theoretical study of the electronic, linear and nonlinear optical properties of CdSe using a pseudopotential plane-wave method. Since local density approximation (LDA) underestimates its band gap, we used the GW approximation method to calculate its quasiparticle band structure and obtain a band gap 1.67 eV in agreement with experimental value. The GW corrected gap was used as scissor shift to calculate the linear and nonlinear optical properties. Our calculations show that the optical absorption edge is located around 1.7 eV. The intraband and interband contributions to the imaginary part of second-order nonlinear optical susceptibility χ333(2)(2ω,ω,ω) are presented over a broad energy range. The calculated result for |χ333(2)(0)| (at zero frequency limitation) is 74 pm/V, which is close to the experimental value 72 pm/V.