Nonlinear Optical Responses of Spin-Coated Vanadium Oxide Films

Abstract

We report on the third-order nonlinear optical responses of V₂O₅ films prepared by pyrolysis of spin-coated films of vanadium 2-ethylhexanoate. Temporal behavior of third-order optical nonlinearity of the spin-coated V₂O₅ films was examined at a wavelength of 532 nm by the degenerate four-wave mixing (DFWM) technique using a mode locked Nd/YAG laser (35 ps fwhm). Fast relaxation with a lifetime of 25 ps and slow relaxation with a lifetime of 150 ps were observed. The nonlinear transmission experiment on the spin-coated V2O5 films using the same laser source showed that the transmittance decreased with increasing intensity of the incident light. The intensity-dependent absorption coefficients (β) were roughly estimated to be 3.5×10⁻⁵ cm/W. Transient absorption properties of the V₂O₅ film were measured by use of the second and third harmonics of a Q switched Nd/YAG laser (10 ns fwhm). The results observed for the nonlinear transmission and the transient absorption suggest that induced absorption would contribute to the third-order optical nonlinearity of the V₂O₅ films with fast response times, and also suggest that the V₂O₅ films have potentiality for use as optical power limiting materials.