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This Letter, reports the focused-femtosecond-laser induced dissolution of gold nanoparticles in an Au+-doped glass. Gold nanoparticles, pre-precipitated in the glass either by thermal treatment or by irradiation of a focused femtosecond laser and successive thermal treatment, are broken to dissolve when they are reirradiated by a focused femtosecond laser. It is suggested that the dissolution of gold nanoparticles is due to dramatically increasing in the temperature of gold nanoparticles, resulting from the energy absorbing from the femtosecond laser. A repeatable process of precipitation and dissolution of gold nanoparticles is also realized anywhere selected inside the glass, so does the control of the size of gold nanoparticles. [Copyright &y& Elsevier]

We report on the precipitation control of Au nanoparticles in periodic arrays in silicate glass. Au[sub 2]O-doped glass samples were first irradiated by two 800 nm interfered femtosecond laser pulses at room temperature and then heat treated at 550 °C for the Au nanoparticle precipitation in the laser irradiation areas. One-dimensional periodic arrays of the Au nanoparticles were controlled by changing the pulse energy and the incident angle between the interfered laser pulses. The smallest dimension in the obtained arrays was a width of 300 nm. The mechanism of the metal nanoparticle precipitation by this technique was discussed. Only two pulses are required to encode these periodic microstructures, which are applicable to emerging nanostructure devices such as optical memory with ultrahigh storage density, micrograting with high diffractive efficiency and integrative micro-optical switches. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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 prepared nano-C60 based insulating oil, which has the potential to overcome the application barriers of nanomodified insulating oil. We find that nano-C60 based insulating oil has an excellent stability. Its electrical performance increases by 17.9%, 9.3%, and 8.3% for AC and positive/negative lightning impulse voltage, respectively. We believe that C60 molecules have a strong capacity to absorb electrons and can capture photons in a streamer, which may weaken photoionization in the streamer and thereby improve the electrical performance of insulating oil. [ABSTRACT FROM AUTHOR]

Abstract: We report on space-selective co-precipitation of silver and gold nanoparticles in Ag+, Au3+ co-doped silicate glasses by irradiation of femtosecond laser pulses and subsequent annealing at high temperatures. The color of the irradiated area in the glass sample changed from yellow to red with the increase of the annealing temperature. The effects of average laser power and annealing temperature on precipitation of the nanoparticles were investigated. A reasonable mechanism was proposed to explain the observed phenomena. [Copyright &y& Elsevier]

Abstract: We report the space selective precipitation of Pd nanoparticles in Pd2+-doped silicate glass by ultrashort laser pulses irradiation and further annealing. Absorption spectra, transmission electron microscopy, refractive index measurement and Z-scan technique demonstrated that metallic Pd nanoparticles were precipitated in the glass sample after irradiation by an 800-nm femtosecond laser and subsequent annealing at 600°C. We discuss a refractive index change and nonlinear absorption that combines the precipitation of Pd nanoparticles. [Copyright &y& Elsevier]

We report on precipitation of Ag nanoparticles in silicate glasses by a femtosecond laser irradiation and successive annealing. Effect of Al2O3 on the precipitation of Ag nanoparticles in glasses was investigated. Absorption spectra show that introducing a small amount of Al2O3 results in inhibition of color centers generation and an apparent increase of the annealing temperature for the precipitation of Ag nanoparticles. The mechanisms of the observed phenomena are discussed. [Copyright &y& Elsevier]

Optical nonlinearities of Au nanoparticles precipitated inside glasses induced by irradiation of a focused femtosecond laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. The transformation behaviors both from self-defocusing to self-focusing and from saturable absorption to reverse saturable absorption were observed in the glass samples, which depend drastically on the irradiation power density of the femtosecond laser used. The optical nonlinearities were analyzed in detail and proved numerically by the excited-state theory of conduction band electrons. [Copyright &y& Elsevier]

Abstract: We report on three-dimensional precipitation of Au nanoparticles in gold ions-doped silicate glasses by a femtosecond laser irradiation and further annealing. Experimental results show that PbO addition plays the double roles of inhibiting hole-trapped centers generation and promoting formation and growth of gold nanoparticles. Additionally, glass containing PbO shows an increased non-linear absorption after femtosecond laser irradiation and annealing. The observed phenomena are significant for applications such as fabrications of three-dimensional multi-colored images inside transparent materials and three-dimensional optical memory, and integrated micro-optical switches. [Copyright &y& Elsevier]