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

Perovskite oxide vanadium-doped SrSnO 3 (SrSn 1− x V x O 3 ) 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 SrSn 1− x V x O 3 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 n 2 , and the open-aperture measurements demonstrate a saturable absorption β . Both the n 2 and β responses vary with the increase of V doping level. The metal-oxygen chemical bond and the localized V 5+ Sn 2+ V 5+ complex contribute to the enhancement of optical nonlinearity, and the highest value of third-order susceptibility χ (3) is observed in SrSn 0.5 V 0.5 O 3 film.