The Study Of The Preparation And Optical Response Characteristics Of Vanadium Pentoxide Thin Films

Vanadium is a transition metal that combines oxygen to form vanadium oxides,of which there are more than ten kinds.Among them,vanadium pentoxide（V₂O₅）is the most stable vanadium oxide with the highest valence of vanadium atoms.It is often used as an energy storage electrode because of its unique layered structure.In recent years,the development of ultrafast lasers has greatly promoted the development of nonlinear optics,a branch of physics,making it one of the most active subject areas in recent years.The essence of nonlinear optics is to explore the interaction between light and matter.Therefore,the main purpose of this paper is to use ultrafast lasers to explore the nonlinear optical response characteristics of energy-saving materials V₂O₅ films.The specific research contents and results are as follows:1.The V₂O₅ film with high crystallinity was prepared on the r-plane sapphire substrate by using radio frequency magnetron sputtering technology.X-ray diffractometer（XRD）,Raman spectrometer and X-ray photoelectron spectroscopy（XPS）were used to measure the structural components of the film.The results showed that the film was a V₂O₅ crystal with layered structure.The surface morphology of the film was observed by atomic force microscope（AFM）and it can be seen that there were nanocrystalline rod-like structures composed of fine grains on the surface of the film.2.The third order nonlinear optical properties of V₂O₅ films were studied using a single-beam Z-scan experimental device.Open-aperture Z-scan curve obtained by the experiment showed that the V₂O₅ film has a saturable absorption characteristic.Fitting the curve to calculate the third-order nonlinear saturated absorption coefficient of V₂O₅ is-338 cm/GW.In addition,the modulation depth of five different thicknesses of V₂O₅ thin films was compared,and it was found that the thickness of the film has a significant effect on its modulation depth.The thicker the film,the greater the depth of modulation.When the thickness of the film is 90 nm,the corresponding modulation depth is up to 29.3%.In addition,the third-order nonlinear refraction coefficient of the V₂O₅ film was measured through a closed-aperture Z-scan experiment.The results showed that V₂O₅ exhibits self-defocusing properties,and its third-order nonlinear refractive index is-3.62×10^-12 cm²/W.3.The ultrafast laser system was used to irradiate the surface of the V₂O₅ film,and then the refractive index change in the irradiated area was qualitatively observed with the aid of a phase contrast microscope.The results showed that the refractive index of the irradiated region decreases compared with that of the unirradiated region.In addition,the influence of single pulse energy,pulse width and repetition frequency on refractive index modification were investigated.With the help of a Confocal Micro-Raman spectrometer,the Raman spectra of the irradiated regions were obtained.The results showed that the variation in refractive index were mainly caused by the change of the density of the V₂O₅ film and the change of the oxidation state.