Nonlinear optical characterization of zinc doped tellurite glasses for optical limiting performance

Abstract

Zinc doped ternary boro-tellurite glasses having composition (100-x) [70 TeO2.30 B2O3].x [ZnO]; x = 4, 8, 12, 16 and 20, have been synthesized via melt quench method. X-ray diffraction pattern confirms the non-crystalline nature of as-synthesized glasses. Fourier Transform Infrared spectra of the synthesized glasses signify the presence of absorption bands associated with the bond mode of vibration and structural units like TeO4, TeO3, BO3 and BO4 present in the glass matrices. The experimental data of absorption coefficient obtained from absorption spectra has been fitted with Davis and Mott’s model to evaluate the optical band gap energies of all the glass samples. The observed decrease in band gap energy is due to increasing number of nonbridging oxygens with increasing concentration of ZnO. Refractive index of glasses has been calculated using band gap. Z- scan technique in open aperture geometry is used to observe the variation of nonlinear optical properties with ZnO content. The experimentally observed data has been fitted with the theoretical models to estimate the value of two-photon absorption (TPA) coefficient β that is found to increase from 1.1524 × 10−10 cm/W to 2.8464 × 10−10 cm/W with increasing ZnO content in the glass matrix. The nonlinear refractive index of the glasses also increase from 1.88 × 10-13 cm2/W to 2.33 × 10-13 cm2/W with increase The optical limiting threshold values have been estimated to predict the limiting behavior of as synthesized glasses. Limiting threshold found to decease with increase in ZnO content to 59 GW/cm2. The optical limiting performance suggests that these glasses serve as suitable optical limiters at ∼ 532 nm.