Study of vibrational spectroscopy, linear and nonlinear optical properties of borate-modified tellurium–silica–bismuthate glasses

Abstract

Quaternary glass system xB2O3−(30−x) SiO2−65Bi2O3−5TeO2 has been prepared by standard melt-quenching technique. The amorphous nature of glass samples has been ascertained by X-ray diffraction patterns. The compositional variations in density, molar volume and crystalline volume have been examined. Analysis of FTIR spectra shows the occurrence of BO3, SiO4 and TeO3 structural units along with both network modifying [BiO6] octahedral as well as network forming [BiO3] pyramidal structural units. The values of indirect and direct band gap energies have been estimated from fitting of experimental data of absorption spectra with Mott–Davis’s model and hydrogenic excitonic model, respectively. Z-scan technique with nanosecond pulsed laser at ~ 532 nm has been carried out to investigate the third-order nonlinear (3ONL) optical properties of prepared glass samples. The values of nonlinear parameters, viz. nonlinear refractive index (n2) and nonlinear absorption coefficient (β), have been estimated by fitting of experimentally observed data with theoretical models, and both are found to decrease with increase in borate content at the expense of silicate content. The 3ONL susceptibility (χ(3)) including real and imaginary parts has been calculated and observed to decrease with increase in borate content.