Modulation of the band gap and enhancement of the third-order optical nonlinearity in vanadium-doped SrSnO3 films

Abstract

Perovskite oxide vanadium-doped SrSnO3 (SrSn1−xV x O3) thin films with different concentrations x=0.1∼0.9 were fabricated by using pulsed-laser deposition, and the effects of V doping on the structure, optical band gap, and the third-order optical nonlinearity were systematically investigated. With the increase of the x value, the lattice parameters of SrSn1−xV x O3 decrease from 3.997 to 3.862Å gradually, while the optical band gaps first increase and then decrease with a boundary at x=0.3. The third-order nonlinear optical responses were studied via the z-scan technique. The closed-aperture measurements show a negative nonlinear refractive index n2, and the open-aperture measurements demonstrate a saturable absorption β. Both the n2 and β responses vary with the increase of V doping level. The metal-oxygen chemical bond and the localized V5+Sn2+V5+ complex contribute to the enhancement of optical nonlinearity, and the highest value of third-order susceptibility χ(3) is observed in SrSn0.5V0.5O3 film.