[en] Al₂O₃ - SiO₂ glasses doped with Sm³⁺ ions were irradiated with an 800 nm wavelength femtosecond laser pulse and the formation of Sm²⁺ ions was investigated. The Sm³⁺ ions were reduced to Sm²⁺ within a few minutes of laser irradiation. Electron spin resonance spectra indicated that the hole was trapped in non-bridging oxygen bound to Al³⁺, while the electron was captured in the Sm³⁺, leading to the Sm²⁺ formation. The thermal stability of the photoinduced Sm²⁺ ions was also investigated by fluorescence spectroscopy. The Sm²⁺ ions were converted to Sm³⁺ ions by heating the glasses in air at 300- 400 deg. C