Genuine two photon absorption and excited state absorption in Fe nanowires decorated β-BaB2O4 nanoplatelets

Abstract

Concentration dependent nonlinear absorption and optical limiting action of Fe nanowires decorated β-BaB2O4 nanoplatelets was studied by Z-scan experiment using Q-switched nano pulsed Nd:YAG green laser. Open aperture Z-scan curves with valley like pattern indicates the existence of reverse saturable nonlinear absorption (RSA). Intensity dependent nonlinear absorption studies shows the Fe concentration dependent transition of genuine two photon absorption (2 PA) to excited state absorption (ESA). Interesting transition to ESA process in 0.05 M Fe decorated β-BaB2O4 arises due to the availability of near-resonant state (trapped defect state, 2.3 eV). Along with transition in nonlinear absorption, incorporation of Fe in β-BaB2O4 enhanced NLO behavior leading to strong optical limiting action than pristine β-BaB2O4. 0.05 M Fe nanowires decorated β-BaB2O4 nanoplatelets possess higher 2 PA coefficient (1.6 × 10−10 m/W) and lower onset limiting threshold (1.03 × 1012 W/m2) and thus ensure its superiority for OL applications. Earlier Fe decorated β-BaB2O4 were prepared by hydrothermal method with three decorating concentration (0.01 M, 0.03 M and 0.05 M). The incorporation and distribution of Fe3+ ions in β-BaB2O4 was confirmed by XRD, EDS and FTIR analysis. FESEM and HRTEM confirm the presence of densely packed nanowires of Fe ions upon BBO nanoplatelets through densification process arising from the strong attractive force of Fe3+ ions. Altogether Fe decorated β-BaB2O4 nanostructure with superior NLO coefficients finds potential application as laser safety devices for widely used 532 nm nanopulsed laser.