Zinc oxide thin films’ nonlinear optical characteristics of thickness of 425 nm were studied throughout the research. Using a laser diode with a wavelength of 650 nm and a low laser power of 2 mW, the well-known Z-scan technique was employed. The measurements were made at various frequencies between 1 kHz and 100 kHz. The results indicate a positive sign for two photon absorption coefficient at both the low and high frequency range. The Kerr coefficient starts with a positive sign at low frequency range that switch to a negative sign when the frequency range gets higher.
