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Rare-earth glasses for new optical applications: microscopic modifications by a femtosecond laser and realization of new optical functions

We report on the observations of novel phenomena in rare- earth-doped glasses induced by an 800 nm femtosecond pulsed laser. 3D long-lasting phosphorescence in various colors was observed in calcium aluminosilicate glasses doped with Ce3+, Tb3+, and Pr3+. After irradiation by the femtosecond laser, the focused part of the laser in the glasses emits bright and long-lasting phosphorescence able to be clearly seen with the naked eye in the dark even one hour after the removal of the activating laser. We also observed permanent photoreduction of Sm3+ to Sm2+ inside a transparent and colorless Sm3+- doped sodium aluminoborate glass. After irradiation by the femtosecond laser, the focused part of the laser in the glass became orange in color. Absorption and confocal photoluminescence spectra showed that a part of Sm3+ was reduced to Sm2+ after the laser irradiation. Photochemical hole burning phenomenon has also been confirmed in the femtosecond laser photoreduced part after the further irradiation by a DCM dye laser. Electron spin resonance spectra of the glasses before and after the laser irradiation have been measured to clarify the mechanisms of these phenomena. Microscopic modifications using a femtosecond pulsed laser is promising to open new field in science and technology of rare-earth-doped materials.