Abstract
Transparent and colorless Sm3+-doped 10Al2O3-5B2O3-85SiO2 glasses were prepared by sol-gel method. The strong absorption band at about 200 nm and weak absorption bands in the range from 320 to 450 nm before the irradiation are assigned to the charge transfer and the 4f-4f transitions of the Sm3+ ions. After irradiation, the increase of the absorption in the range from the UV to visible region is associated with the formation of defect and Sm2+ ions. The emission spectrum of the glass under 337 nm N2 laser excitation before irradiation consists of the four bands coming from 4G5/2-6H5/2, 6H7/2, 6H9/2, 6H11/2 transitions of the Sm3+ ions, respectively. After irradiation, the emission spectrum under the same excitation condition shows the stronger emission band at about 686 nm assigned to the 5D0-7F0 transition of the Sm2+ ions and the weaker bands of the Sm3+ emission. These results reveal that some Sm3+ ions were reduced to Sm2+ ions via femtosecond laser irradiation. The emission band of the Sm2+ ions by photo-induced show red shift, compared with the emission of the Sm2+ by reduction with H2 gas. The mechanism of the photo-induced reduction of Sm3+ ions is discussed based on optical properties.
