Abstract
An effective-medium theory (EMT) is developed to predict the effective permittivity of dense random dispersions of high optical-conductivity metals such as Ag, Au, and Cu. Dependence of on the volume fraction , a microstructure parameter related to the static structure factor and particle radius , is studied. In the electrostatic limit, the upper and lower bounds of correspond to Maxwell–Garnett and Bruggeman EMTs, respectively. Finite size effects are significant when becomes , where , , and denote the nanoparticle polarizability, wavenumber, and matrix refractive index, respectively. The coupling between the particle and effective medium results in a red-shift in the resonance peak, a nonlinear dependence of on , and Fano resonance in .
©2012 Optical Society of America
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