We present optical properties of aluminum oxide (Al2O3) thin films. A high quality Al2O3 films fabricated by sol-gel (dip-coating) method were grown on quartz substrates at temperature equal to 25 °C (RT) for 30 min inside the chamber. Next, a part of prepared samples was annealed for 12 h at fixed temperature equal to 500 °C. The rest of samples were left in the normal condition. This procedure can be repeated after each layer deposition.
The transmission spectra were measured in range 200 – 2000 nm to investigate the optical and structural properties. Third harmonic generation measurements were performed by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm in picosecond regime for investigations of the nonlinear optical properties. The obtained values of second and third order nonlinear susceptibilities were found to be high enough for the potential applications in the optical switching devices based on refractive index changes. Presented spectra confirm high optical quality of the investigated zinc oxide thin films.