Laser-controlled precipitation of gold nanoparticles in silicate glasses

We report on the observation of space-selective precipitation of gold nanoparticles in Au2O-doped silicate glass by a method of irradiation with an 800-nm femtosecond laser and further heat treatment. The irradiated region of the glass first became gray in color after irradiation with the femtosecond laser and then turned red after further heat treatment at around 520 degreesC, indicating that gold nanoparticles have precipitated in the irradiated region of the glass. A possible mechanism has been suggested that the Au+ ions in the region irradiated are reduced to Au-0 atoms by the femtosecond laser, and then the Au-0 atoms accumulate to form gold nanoparticles with the glass sample heat treated. The observed phenomenon should have potential applications in the fabrication of ultrafast all-optical switches.