Nonlinear optical properties of Cu nanoparticles embedded in insulators by high-current Cu- implantation

Optical properties including nonlinear susceptibility and response were investigated for insulators with embedded nanoparticles fabricated by ion implantation. Negative ion implantation at various dose rates has been applied to generate the Cu nanoparticles in amorphous and crystalline SiO2. Optical absorption strongly depended on the dose rate, ranged from 1 to 100 mu A/cm(2), being influenced by a sputtering effect, radiation damage and an annealing effect of irradiation. Third-order optical susceptibility, evaluated with the degenerate four-wave mixing, yielded values of 1-2 x 10(-8) esu in good correlation with the absorbance. Transient absorption was also measured with the pump-probe method using a femtosecond laser system. The time-resolved differential optical density of as-implanted samples decayed within 10 Ds more slowly than that of annealed ones. The slower decay was attributed to the slower energy transfer from the electron to the phonon system, in the as-implanted particles. (C) 2000 Elsevier Science B.V. All rights reserved.