近赤外フェムト秒レーザー照射により誘起されたナトリウムホウ酸塩ガラスにおけるSm^<2+>の光化学ホールバーニング Photochemical Hole Burning of Sm^<2+> in Sodium Borate Glasses Induced by Near-Infrared Femtosecond-Laser Irradiation

We report on photochemical hole burning of Sm^<2+> in sodium borate glasses irradiated with femtosecond- laser pulses of 800 nm wavelength. The irradiation of Sm^<3+> -doped sodium borate glasses with femtosecond-laser pulses causes electron-trapped Sm^<3+> i.e., Sm^<2+> and point defects such as an oxygen hole center and an electron trapped near Na^+. The measurements of spectral hole burning were carried out for the ^5D_0-^7F_0 transition of Sm^<2+> using a DCM dye laser. Photoionization hole burning is observed at 77 K to room temperature for the glasses exposed to femtosecond-laser pulses, and also for the glasses prepared by melting under reducing conditions. The hole-burning efficiency of Sm^<2+> produced by the photoinduced process is about twice higher than that by the thermal process. It is thought that the metastable Sm^<2+> ions and oxygen hole centers induced by femtosecond-laser irradiation are responsible for the observed phenomenon. We propose that the efficient photoionization hole burning is caused by the photostimulated recombination of the electron trapped by Sm^<3+> with the oxygen hole center.