Visible optical nonlinearity of vanadium dioxide dispersions

Vanadium dioxide (VO₂), a correlated oxide compound, is one of the functional materials extensively studied in solid state physics due to its attractive physical properties. However, the nonlinear optical response of VO₂ and related all-optical applications have been paid less attention. Here, the nonlinear refractive index (n ₂) and third-order nonlinear susceptibility (χ ⁽³⁾) of VO₂ dispersions have been acquired to be 3.06 × 10^-6 cm² W^-1 and 1.68 × 10^-4 esu at a wavelength of 671 nm, and 5.17 × 10^-6 cm² W^-1 and 2.83 × 10^-4 esu at a wavelength of 532 nm via the spatial self-phase modulation (SSPM) and spatial cross-phase modulation (SXPM) effects in the visible regime, respectively. Based on the excellent nonlinear optical properties of VO₂ dispersions, the proof-of-principle functions such as optical logic or-gates, all-optical switches, and inter-channel information transfer are implemented in the visible wavelength. The experimental results on the response time of VO₂ to light indicate that the formation of diffraction rings is mainly an electronically coherent third-order nonlinear optical process. The experimental results show that the VO₂ dispersions exhibit an excellent nonlinear optical response and may lay the foundation for the application of VO₂-based all-optical devices.