Structural change in Au3+-doped BK7 glass irradiated by femtosecond laser

We report on structural change in an Au3+-doped BK7 glass irradiated by an infrared femtosecond laser at 800 nm. A grating structure is inscribed in the glass sample. The glass sample is then annealed at various temperatures. Structural change of the grating is observed by an optical microscope. Absorption spectra indicate that colour centres are induced after the laser irradiation, and they decrease with increasing annealing temperature. An nanoparticles are precipitated at high temperatures (>= 600 degrees C). The mechanisms of the phenomena are discussed.