Optical properties and valence change of samarium ions in a sol–gel Al2O3–B2O3–SiO2 glass by femtosecond laser irradiation

Abstract 10Al 2 O 3 –5B 2 O 3 –85SiO 2 – x Sm 2 O 3 glasses were prepared by the sol–gel method. The emission spectra of the glasses indicate that the quench concentration of the Sm 3+ ions is about 0.2 mol%. The emission spectra of the glasses after high-temperature treatment with H 2 gas exhibit the coexistence of the Sm 3+ and Sm 2+ ions. We observed the strong emission line of the Sm 2+ ions and the emission band of the non-bridging oxygen hole center when the glasses were exposed to a femtosecond laser. It indicates that some Sm 3+ ions were reduced to Sm 2+ ions by femtosecond laser pulses and non-bridging oxygen hole centers were formed. The 5 D 0 – 7 F 0 emission line of the Sm 2+ ions by femtosecond laser irradiation shows a red shift, compared with the emission of the Sm 2+ ions by reduction with H 2 gas. The strong absorption band and weak, sharp absorption lines in the range from the UV to IR come from charge transfer and the transition from the 6 H 5/2 state to the various excited states of the Sm 3+ ions. The reduction mechanism of Sm 3+ ions is discussed.