<title>Laser-induced bleaching of insulators under MeV heavy-ion implantation</title>

High-energy ion implantation is one of the unique methods to fabricate nano-scale structures, taking advantage of the spatial controllability and the non-equilibrium atomic injection. Metal-ion implantation into a transparent insulator creates a metal nanoparticle composite, which is promising as a nonlinear optical material with ultrafast response. Radiation damage of substrates and/or nanoparticles, which is inherent in ion implantation, is a drawback for optical performance of the nanoparticle composites. It is desired to annihilate radiation damage without melting the matrix. We have applied laser irradiation of sub-gap energy during heavy-ion implantation. Copper ions of 3 MeV and laser of a sub-gap energy (2.3 eV) irradiated insulators of a-SiO2 and spinel MgO"2.4(Al2O3). The dose rate varied up to 10 (mu) A/cm2 for Cu ions of 3 MeV and up to 0.2 J/cm2"pulse at 10 Hz for YAG-SHG laser. Only when ions and photons were simultaneously irradiated at the higher photon intensity (> 0.1 J/cm2"pulse), the insulators were effectively bleached in the optical absorption spectra. As well as the bleaching, precipitation enhancement and atomic desorption took place. The results indicate importance of dynamical electronic excitation during ion irradiation and that the photon irradiation enhances atomic displacements either at the surface or in the bulk.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.