Research on the response characteristics of vanadium pentoxide film to the irradiation of ultrafast pulsed laser

Vanadium pentoxide (V₂O₅ ) is the most stable phase among many transition metal vanadium oxides, and has already been widely used in many fields. In this study, the morphological, structural, and optical responses of V₂O₅ film to ultrafast laser irradiation was investigated. The third-order nonlinear optical properties of V₂O₅ film were measured by common Z-scan technique, and the results showed that V₂O₅ film has self-defocusing and saturable absorption characteristics. The third-order nonlinear absorption coefficient and nonlinear refractive index were calculated to be −338 cm/GW and −3.62 × 10⁻¹² cm²/W, respectively. The tunable saturated absorption with modulation depth ranging from 13.8% to 29.3% was realized through controlling the thickness of vanadium pentoxide film. V₂O₅ film was irradiated by ultrafast laser with variable pulse energy, and the morphological and structural responses of the V₂O₅ to the laser with different energy densities were investigated. The irreversible morphological and structural responses of V₂O₅ films to ultrafast laser irradiation was analyzed using the phase-contrast microscope and Raman spectrum. The chemical structure change from V₂O₅ to V₆O₁₃ was considered the main reason for refractive index modification.