关键词: local dielectric resonance, effective linear optical response, nanometre metallic cluster

Abstract: Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances $\varepsilon$₁ and $\varepsilon$₂. Through varying the difference admittance ratio $\eta [ = (\varepsilon _2 - \varepsilon_0 ) / (\varepsilon _1 - \varepsilon _0 )]$, we find that their optical responses are determined by the local resonance. There is a blueshift of absorption peaks with the increase of $\eta$. Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances, we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-component composites $\varepsilon _{\rm e} = \varepsilon _0\bigl(1 + \sum_{n = 1}^{n_{\rm s} } [({{\gamma _{n_1 } + \eta \gamma_{n_2 } })/({\varepsilon _0 (s - s_{n} )})]} \bigr)$, and the sum rule of cross sections: $\sum_{n = 1}^{n_{\rm s} } {(\gamma _{n_1 } +\eta \gamma _{n_2 } ) = N_{h_1 } + N_{h_2 } } $, where $N_{h_1}$ and $N_{h_2}$ are the numbers of $\varepsilon _1 $ and $\varepsilon _2$ bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.

Key words: local dielectric resonance, effective linear optical response, nanometre metallic cluster