Laser-induced defect centers and valence state change of Mn ions in sodium borate glasses

In this report, an ultrafast laser was used to produce persistent change of valence states of Mn ions in sodium borate glasses. Glass composition of sodium borate in this study was 85B2O3-15Na2O. We observed a broad emission at 600 nm of the transition 4T1-6A1 of doped Mn2+ ions with excitation at 325 nm in an unirradiated area. Femtosecond laser irradiation produced additional strong blue emission at 440 nm and reduced the emission intensity from Mn2+ ions. The irradiation produced the absorption band of Mn3+ at 550 nm, resulting in color change of the glass. The blue band was measured as a function of irradiation exposure for samples with various concentrations of Mn ions. The valence state change of Mn2+ to Mn3+ was suppressed in Mn and Cr codoped glasses.