Nonlinear optical performance and optical limiting of germanate glasses modified with PbF2 and B2O3 induced by nanosecond pulsed laser

In this work, GeO2 modified with PbF2 and B2O3 glasses were synthesized by conventional melting and quenching technique to investigate the effect of modifier network on its linear and nonlinear optical properties. Linear optical analysis was indicated decreased band gap energy (-0.14 eV) and Urbach energy (-0.12 eV) with increasing of Pb/B molar ratio in the glass structure. Beside, decreasing Urbach energy with increase of Pb/B molar ratio indicated that the increasing large atomic radius in the glass matrix led to accumulation of the defect states localized inside the band gap. Open aperture Z-scan results exhibited that the germanate glasses had decreasing normalized transmittance and increasing nonlinear absorption coefficient with increasing of the Pb/B molar ratio. The higher optical limiting effect was in line with the nonlinear absorption behaviors of the germanate glasses. These observations are associated with increased two-photon and free-carrier absorptions with increasing of the PbF2 modifier content which led to the reduction of the band gap energy and changing distribution of the localized defect states which facilitate the nonlinear absorption. Our results indicate that 70GeO2 + 20PbF2 + 10B2O3 glasses are very good candidate as optical limiter applications in optoelectronic applications.