Theoretical and Experimental Study of the Optical and Nonlinear Optical Properties of TlInS2 Crystals of Hexagonal Modification

The electronic band structure, origin of energy states, spectral dependences of optical functions at different polarizations of incident light and partial densities of states projected onto atoms have been studied for TlInS₂ crystals of hexagonal modification using ab initio calculations. The linear and nonlinear optical properties of this compound were experimentally investigated in the range of photon energies from 0.7 to 6.5 eV by spectral ellipsometry. The experimentally found spectral dependences of the imaginary and real parts of the dielectric function; optical conductivity; refractive indices; and extinction and absorption coefficients are in good agreement with the calculation results. The nonlinear refractive index, as well as the first- and third-order nonlinear susceptibilities, were calculated; the found values indicate good prospects of integrating the compound under study into various nonlinear optical systems.