Structural, linear and enhanced third-order nonlinear optical properties of Bi12SiO20 nanocrystals

This paper reports the structural, linear and nonlinear optical properties of bismuth silicon oxide (BSO) nanocrystals with grain size from 60 to 150 nm synthesized by chemical solution decomposition (CSD) method. The X-ray diffraction, FTIR, and micro Raman studies revealed the formation of pure single phase cubic structured BSO nanocrystals at 700 °C of calcination temperature. TEM studies have confirmed the size and the presence of crystalline phase of the BSO nanocrystals. Linear optical properties studied through the UV–visible spectrum showed the presence of a “blue shifted” peak around 270 nm corresponding to a band gap of 4.6 eV due to the formation of nanophase crystals. The nonlinear optical properties studied using a standard open aperture z-scan showed strong nonlinear absorption both with nanosecond and picosecond pulsed excitations. In addition to the nonlinear absorption mechanism, nonlinear scattering was also observed to contribute to the reverse saturable absorption (RSA) behavior leading to a very high RSA behavior in both the time regimes.