Modeling and optical characterization of γ-irradiated Cu2+Doped borate glasses as bandpass optical filters

Abstract

Novel systems of alkali borate glasses with various CuO concentrations from 0.2 up to 1.5 mol% have been prepared by the conventional melt-quenching technique. Several optical, physical, and structural characteristics of the prepared glasses have been examined before and after incremental γ-irradiation doses. The intensity of the blue color of the glasses is controlled by CuO concentrations, with Cu+/Cu2+ in ionic equilibrium. UV/Vis absorption peaks centered at 740 nm can be correlated to a tetragonal twist of the octahedral structure due to 2B1g-2B2g electronic transition. Photoluminescence (PL) extinction spectra can be attributed to Cu+-Cu+ energy migration after Cu+→ Cu2+ energy transfer. Electron spin resonance (ESR) measurements show sharp signals at magnetic fields ranging from 3344 to 3326 Gauss (g = 2.08–2.09), corresponding to the divalent copper state (Cu2+) in octahedral units. FTIR spectra revealed stable structures towards irradiation. Either an increase in CuO content or irradiation led to greater UV absorption, lower PL intensity, lower bandgap (Eopt), lower density, larger molar volume, and slightly more intense ESR signals. Copper ions can be considered as modifiers since they increase the degree of disorder in the glassy network. UV/NIR band stop, FWHM, and center of peaks confirmed the high efficiency of the prepared Cu-doped glasses as colored optical bandpass filters in the green and near-blue regions for UV/IR light laser protection.