Evaluation of the limits of resonance tunability in metallic nanoshells with a spectral averaging method

Spectral selectivity based on tuning the surface plasmon resonance in metallic nanoshells by variation of the relative shell thickness is shown to be limited by the interplay between scattering and absorption, To achieve resonance energies in the near infrared and infrared, relatively large cores are needed, which lead to strong and broad scattering bands and multipolar contributions in the visible, The scattering contribution to extinction is described with a new parameter S., which is defined for a wavelength range of interest V This parameter can help in designing materials for specific applications where scattering is either hindering, as in near-infrared absorbers for visually clear windows, or actually desired, such as in particle-array-based sensors. (C) 2005 Optical Society of America.