Photoreduction of Ag + in aluminoborate glasses induced by irradiation of a femtosecond laser
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Jianrong Qiu Photon Craft Project, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences and Japan Science and Technology Agency, Kyoto 619-0237, Japan
Yasuhiko Shimotsuma, Koji Fujita, and Kazuyuki Hirao Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan (Received 21 September 2004; accepted 24 November 2004)
We report on photoreduction of Ag+ in aluminoborate glasses induced by irradiation of a femtosecond laser. Novel fluorescence was observed in the femtosecond laser irradiated glass when excited by a 365 nm ultraviolet lamp. Optical absorption, emission, and electron spin resonance spectra of the glass samples demonstrated that after the laser irradiation, portions of silver ions near the focused part of the laser beam inside the glass were reduced to silver atoms, which resulted in the formation of the characteristic fluorescence. The observed phenomenon may have promising applications in the fabrication of functional optical devices.
I. INTRODUCTION
The properties of noble metal doped glasses have been extensively studied because of their unique optical behaviors such as large third-order nonlinear susceptibility and ultrafast nonlinear response.1,2 Metal ion or nanoparticle doped glasses are expected to be applicable materials for the fabrication of optical waveguides and waveguide lasers,3 ultrafast all-optical switches,4 and optical disk data storage.5 In all these applications, the controllable valence state and nanoparticle size of noble metals are essential. Recently, photosensitivity induced by irradiation with femtosecond laser pulses into optical materials has attracted much attention because of their potential applications to functional optical devices.6–10 The reason for using this laser is that its electric-field intensity can reach 100 TW/cm2 by the use of a focusing lens, which is sufficient for inducing nonlinear optical effects in materials.11 The photoinduced reaction is expected to occur only near the focused part of the laser beam due to nonlinear optical processes.
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0076 644
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 3, Mar 2005 Downloaded: 15 Mar 2015
Herein, we report on a characteristic fluorescence excited by a conventional 365 nm ultraviolet (UV) lamp in Ag+-doped soda-alumino-borate glass after exposure to a focused femtosecond pulsed laser. We observed the photoreduction of the Ag+ ions to Ag0 atoms in glass by focusing 120-fs laser pulses through a microscope objective lens. We measured optical absorption, emission, and electron spin resonance (ESR) spectra of the glasses before and after laser irradiation, as well as after further annealing at various temperatures. The mechanism of the photoreduction of Ag+ in the glass is discussed. The present research provides a method by which the generation and disappearance of a characteristic fluorescence in borate glass can be contr
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