Theoretical studies of plasmon resonances in one-dimensional nanoparticle chains: narrow lineshapes with tunable widths

In this paper we describe a new configuration for producing narrow extinction lineshapes for light scattering from one-dimensional arrays of silver nanoparticles. In this configuration, which is specifically concerned with an array with a finite number of relatively large ( radius greater than around 30 nm) nanoparticles, the wavevector of the light is chosen to be parallel to the array axis, while the polarization direction is perpendicular to the array axis. This leads to narrow plasmon/photonic lineshapes when the particle spacing is half the incident wavelength. This effect stands in contrast to the narrow lines previously found for wavevector and polarization vector perpendicular to the array axis, where the optimum spacing is close to the wavelength. The results are rationalized using a semi-analytical evaluation of the coupled dipole interaction, and it is demonstrated that the parallel and perpendicular chains have very different dependence on the number of particles in the chain. Results as a function of chain orientation relative to the wavevector are also considered, as is the possibility of sensing using an array configuration that combines the parallel and perpendicular chain directions.