Optical bistability in TiO2 nanoparticles

Abstract In this paper, experimental results concerning the optical bistability of a colloidal solution of 70–90 nm TiO2 nanoparticles are studied. A CW He–Ne laser beam (with 48 mW output power) was used to interact with a vertical Fabry–Perot interferometer containing a nonlinear sample and the experiment repeated for different thicknesses of the sample. Experiments obtained hysteretic loops due to optical bistability and results were fitted with theoretical curves. The intensity inside the resonator changed at interval 1400–2000 W/cm2. At 632 nm wavelength, nonlinear refraction and absorption indices were obtained as n2 = −8.22 × 10−8 cm2/W and β = 7.5 × 10−4 cm/W using the z-scan method (at I0 = 1415 W/cm2) and have been used in numerical curves of hysteretic loops. Evaluations showed that optical bistability could be considered as a dispersive one.