Metal nanoparticle array waveguides: Proposed structures for subwavelength devices

Taking advantage of the coherent coupling among metal nanoparticles in a one dimensional array, and using partial illumination of the array, we propose a waveguide device which can excite particles in the dark with high efficiency. These array structures enable the propagation of plasmonic excitation for hundreds of microns. The results are based on coupled dipole approximation calculations, and there are important constraints on particle size, spacing and array size to produce these effects. The simulation shows that the incident wave vector can be rotated 90 degrees using a chain structure in which the illuminated particles are spaced by slightly larger than the wavelength and the not-illuminated particles are spaced by approximately half the wavelength. We show that the near-fields around the not-illuminated particles can be ten times higher than around the illuminated particles for appropriately chosen array structures.