Compositional and optical characterization of B2O3–Bi2O3–ZnO–BaO glasses for nonlinear optical applications

B 2 O 3 –Bi 2 O 3 –ZnO–BaO (BBiZBa) glasses with varying Bi 2 O 3 content were prepared by the conventional melt-quenching technique to elucidate composition–property relationships relevant to nonlinear optics. Structural features were assessed using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, confirming predominantly amorphous glass formation across the series. Optical absorption was analyzed by ultraviolet–visible spectroscopy, and the optical band gap (E g ) was determined from Tauc analysis. Increasing the Bi 2 O 3 content systematically reduces E g , indicating a modification of the band structure associated with compositional restructuring of the glass network. Nonlinear optical parameters were evaluated from the linear optical constants, revealing an increase in the third-order nonlinear optical susceptibility ( χ 3 ) with Bi 2 O 3 incorporation. These results demonstrate that Bi 2 O 3 -enriched BBiZBa glasses provide a promising compositional route toward enhanced nonlinear optical response, supporting their potential use in nonlinear optical and photonic device applications.