Third-harmonic optical process in Zn:NiO thin films under the influence of femtosecond and continuous wave laser excitation

Abstract

In this study, we focused on the impact of nonlinear optical properties on Zn-doped NiO thin film, which was analyzed using z scan and THG technique. The z-scan technique was performed using a continuous wave laser. The open aperture shows that all films exhibit the reverse saturable absorption and the mechanism responsible for two-photon absorption, excited state absorption, and free carrier absorption. The closed aperture results in the negative nonlinear refraction caused by the thermal effects. The enhancement in the third-order susceptibility from 5.37 ×10-3 to 13.24 ×10-3 esu with Zn doping is due to the presence and increase in the concentration of defect levels in the films. The THG studies were performed using femtosecond and nanosecond lasers and revealed that the enhancement in the signal with the rise in Zn doping concentration was attributed to the enhancement of photoexcitation and relaxation processes within the sample. These results suggest that Zn-doped NiO films have significant potential for applications in the realm of optoelectronic applications.