Ab initio calculations of the electronic, linear and nonlinear optical properties of zinc chalcogenides

We report calculations of the electronic, linear and nonlinear optical properties of ZnX (X=S, Se, Te) compounds using the full potential linear augmented plane wave (FP-LAPW) method. We present results for the band structure, density of states, and imaginary part of the frequency-dependent linear and nonlinear optical response. Our calculations show that the energy band gap of these compounds decreases when S is replaced by Se and Se by Te. This can be attributed to the increase in the bandwidth of the conduction bands. Our calculated ε2(ω) shows good agreement with the experimental data. We find that the intra- and inter-band contributions of the second harmonic generation increase when moving from S to Se to Te. The smaller energy band gap compounds have larger values of χ123(2)(0) in agreement with the experimental measurements and other theoretical calculations.