Effect of thickness on nonlinear optical properties of EZO thin films

Abstract

In the present work, the effect of thickness on the nonlinear optical properties of Erbium-doped zinc oxide (EZO) films has been investigated. Erbium-doped zinc oxide (EZO-doping concentration of 0.4 wt%) ‘thin films’ of variable thickness were prepared by a spin coating method. The film thickness varied from 92–365 nm. EZO (0.4 wt%) samples were analyzed using Scanning Electron Microscopy (SEM), UV–vis-NIR spectroscopy, and x-ray diffraction (XRD). The z-scan method was applied to measure non-linearity for closed and open aperture configurations. The deposited films were found to have a significant growth orientation along the plane of (002). The deposited films satisfy two-photon absorption as indicated by the minus sign of n2. The values of third-order nonlinear optical susceptibility for the EZO (0.4 wt%) thin film sample were found in the range of 10–6 esu. The Erbium-doped ZnO (0.4 wt%) sample exhibited the best nonlinear behavior at a thickness of 280 nm (β = 8.90 × 10–6 cm W−1, n2 = −5.29 × 10–5 esu, (3) = 14.7 × 10–6 esu). The samples under investigation should pave the path for designing high-order optical limiter devices.