Linear and nonlinear optical properties of ZnO thin films deposited by pulsed laser deposition

This paper presents the structural and optical properties of ZnO thin films deposited by using pulsed laser deposition technique on quartz substrates. The deposition process was carried out at various temperatures of the substrates from room temperature to 825 K in order to investigate these properties of the films and their mutual influence. The structural and morphological properties of the films were investigated by X-Ray Diffraction and Atomic Force Microscopy measurements, respectively. The quality of the films was improved with an increase of the substrate temperature. The linear optical properties of the films were studied by classic and time-resolved photoluminescence spectra in the broad range of the temperature from 13 K to 325 K. Classic photoluminescence measurement allowed us to estimate band gap energy as a function of the temperature. An innovative time-resolved photoluminescence technique lets us precisely measure the decay time in the real time. Results of these measurements reveal a simple exponential decay behavior typical for well oriented crystalline thin films. Presented spectra confirm high structural and linear optical quality of investigated films. The nonlinear optical properties of the films were investigated by Third Harmonic Generation technique. Our results also indicated that the substrate temperature strongly affected nonlinear optical properties and the values of third order nonlinear susceptibilities were found to be high enough for the potential applications in the optical switching devices.