Controlling optical responses through local dielectric resonance in nanometre metallic clusters

Optical responses in dilute composites are controlled through thelocal dielectric resonance of metallic clusters. We consider twolocated metallic clusters close to each other with admittancesvarepsilon₁ and varepsilon₂. Through varying thedifference admittance ratio eta [ = (varepsilon₂- varepsilon₀) / (varepsilon₁- varepsilon₀)], we find that theiroptical responses are determined by the local resonance. There is ablueshift of absorption peaks with the increase of eta.Simultaneously, it is known that the absorption peaks will beredshifted by enlarging the cluster size. By adjusting thenano-metallic cluster geometry, size and admittances, we can controlthe positions and intensities of absorption peaks effectively. Wehave also deduced the effective linear optical responses ofthree-component composites varepsilon_e= varepsilon₀bigl(1 + sum_n=1^{n_s} [(gamma_n2+ eta gamma_n2)/({varepsilon₀(s - s_n))]} bigr), and the sumrule of cross sections: sum_n=1^{n_s} {(gamma_n2+eta gamma_n2 ) = N_h1+ N_h2, where N_h1andN_h2 are the numbers of varepsilon₁ and varepsilon₂ bonds along the electric field, respectively. These results may bebeneficial to the study of surface plasmon resonances on a nanometrescale.