Reverse saturation absorption of CaWO4 and Ce3+ substituted CaWO4 growth on rGO sheets an 2D/3D nanocomposite for smart filtering optical radiation

Abstract

The CaWO4, CaWO4/rGO and Ce3+:CaWO4/rGO nanocomposites are synthesized and subjected to hydrothermal treatment. The optical filtering behavior of materials was explored using reliable Z-scan analysis. It utilizes the focused Gaussian beam of He:Ne laser (632.8 nm) in a continuous wave regime. Closed aperture Z-scan analysis of the synthesized samples exhibits negative refraction evident from the pre-focal peak to post-focal valley. The explicit third order nonlinear parameters such as kerr nonlinearityΔn = 5.6 x10-7 (W/cm2), two photon absorption β = 2.3 x10-4 (W/cm) and optical susceptibility χ3 = 10.5 x10-8 esu were obtained for the Ce3+:CaWO4/rGO (5 wt%) nanocomposites. Ce3+:CaWO4 micro dumbbells grown on the sheets of rGO is observed using HRSEM and HRTEM images. The C 1 s spectra recorded from XPS displays the area of sp2 hybridized (CC) graphitic like structure increases which enhances the optical nonlinearities. Id/Ig ratio increases by increasing the addition of rGO signifies the reduction of oxygenated functional groups in the nanocomposite evidenced by Raman spectra analysis. The bandgap calculated from the Tauc-plot relation is found to be around 3.0 eV and it decreases to 2.9 eV when the wt.% of rGO is increased.