Optical transitions from hexavalent chromium in lithium-borate glasses

The melt-quenching technique was used to prepare a series of chromium-doped borate glasses with the composition xCr2O3–(70 ? x) B2O3–30 Li2O–(x = 0, 0.1, 0.2, 0.3 and 0.5 mol %). low-doping level here employed allowed unambiguously identify well-defined near-edge Cr6+ optical transitions, precisely determine band gap glass host. Additional Cr3+ transitions were observed in visible regime, rendering strong modulation color, from colorless dark greenish, Cr content. Both (after charge transfer transformation into Cr5+) Cr3+oxidation states their variations doping identified electron spin resonance spectroscopy. All samples exhibit similar vibrational spectra dominated by BO3 BO4 structural units, development weak vibration doping. present study provides structurally but optically active tunable hosts suitable for various applications.