Gain and loss of propagating electromagnetic wave along a hollow silver nanorod

Using the discrete dipole approximation (DDA) method, we examined the electromagnetic wave propagation along a hollow silver nanorod with subwavelength dimensions. The calculations show that light may propagate along the hollow nanorod with growing intensities. The influences of the shape, dimension, and length of the rod on the resonance wavelength and the enhanced local electric field, |E|(2), along the rod were investigated. The resonance wavelength monotonically red-shifted with increasing rod dimension perpendicular to the polarization direction. The resonance peak initially shifted to blue with increasing rod dimension parallel to the polarization direction and eventually shifted to red after a threshold value. For the hollow rods with similar cross sections, the square and rectangular rods produced greater enhanced electric fields along the rods. For the rectangular hollow rods with a fixed 10 nm thick shell and 100 nm long edge perpendicular to the polarization direction, light propagates along the outer surface of the rods when the parallel edge length is larger than 50 nm. The propagating wave with higher intensities is confined inside the hollow rods when the parallel edge length is less than 50 nm.