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We report the precipitation and control of metal nanoparticles inside transparent glasses. An Ag[sup +]-doped silicate glass sample was first irradiated by using an 800 nm femtosecond laser at room temperature and then annealed at 550 °C. The area near the focal point of the laser beam became gray after laser irradiation and yellow after further annealing at 550 °C for 10 min. Absorption and electron spin resonance spectra of the glass sample showed that a portion of silver ions near the focused part of the laser beam inside the glass were reduced to silver atoms after the laser irradiation. These silver atoms aggregated to form nanoparticles after further annealing at temperatures above 500 °C. A mechanism is suggested that consists of multiphoton reduction, which is induced by the fundamental light of the laser beam and supercontinuum white light, and diffusion of silver atoms driven by heat energy to form nanoparticles. The observed phenomenon may have promising applications for the fabrication of three-dimensional multicolored images inside a transparent material and for integrative micro-optical switches. [ABSTRACT FROM AUTHOR]

We report the observation of space-selective oxidation of Mn[sup 2+] to Mn[sup 3+] in a transparent and colorless Mn and Fe ions codoped silicate glass at room temperature by using an 800-nm-femtosecond laser. Difference absorption spectrum of the glass after and before the irradiation of the focused infrared femtosecond pulsed laser showed that a portion of Mn[sup 2+] ions near the focused part of the laser beam inside the glass were oxidized to Mn[sup 3+] ions after the laser irradiation. Mn[sup 3+] ions were stable at the temperatures below 300 °C. It is suggested that Mn[sup 2+] ions act as hole trapping centers while Fe[sup 3+] ions as well as active sites in the glass matrix act as electron trapping centers. A promising application was demonstrated for the fabrication of three-dimensional colored image inside a transparent material. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]