Optical nonlinearity of metal nanoparticle composites fabricated by negative ion implantation

Optical absorption and nonlinear absorption were studied for Ag nanoparticle composite. Negative Ag− ion with 60 keV were applied for implanting into amorphous-SiO2 at a flux 3 μA/cm2 to total fluences ranging from 3 × 1016 to 1 × 1017 ions/cm2. Absorption spectra of Ag-implanted amorphous-SiO2 showed a surface plasmon peak resulting from formation of nanoparticles. The strength of the resonance reflected from the local electric field inside the nanoparticle induced by an external electric field. Nonlinear optical constants were evaluated by the z-scan method with a tunable femtosecond laser system. The strength of the nonlinearity also reflected from the local electric field. Nonlinear absorption coefficients exhibit a maximal value of −3.6 × 103 m/GW for Ag:SiO2 at 420 nm (2.95 eV), around the surface plasmon resonance.