Effect of roughness on third-order nonlinear-optical susceptibility of rare earth doped zinc oxide thin films

Zinc oxide (ZnO) and erbium doped zinc oxide (ZnO:Er) thin films, were deposited on heated glass substrates using spray pyrolysis technique. Third-order nonlinear-optical properties of ZnO and ZnO:Er have been investigated by the third harmonic generation (THG) method at the wavelength of 1064 nm using nanosecond Nd³⁺:YAG laser radiation. The dependence of third order nonlinear susceptibility and transmission characteristics on the thin film roughness has been measured. Third order nonlinear optical susceptibility ( chi⁽³⁾) values of the studied materials were in the remarkable range of 10^-12 esu. The deposited films have been analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM).