Optical properties of boro-germanate glass systems

Three samples of boro-germanate glass system (GeO2-B2O3) were prepared by cooling the melt from 1473 degrees K in the compositional series containing 40, 35 and 30 mol% B2O3 For these glasses the optical absorbance, % transmission, optical band gap, relative permittivity (Er), index of refraction (n) and index of dispersion (Abbe No., V-d) have been determined. The position of the absorption edge and hence the optical band gap (E-opt) was found to depend on glass composition. The absorption edge was attributed to indirect transitions. The values of E-opt and n(d) were observed to decrease with increasing B2O3 content while epsilon(r) and V-d increased with increasing B2O3 content.