Resonant channeling of light near metal surface by passive and active silicon nanoparticles

Abstract

We investigate the optical response of passive (homogeneous) and active (doped by a magnetic-dipole source) silicon nanospheres placed above the gold substrate supporting excitation and propagation of surface plasmon polaritons (SPPs). In the case of the passive system, the influence of the particle electric and magnetic dipole resonances on the channeling of scattered light into the two channels: light-into-light and light-into-SPPs, is studied around the telecommunication wavelength range. Scattering efficiencies of both channels are analytically and numerically calculated and compared for different gaps between the nanosphere and gold substrate. Conditions, under which the resonant distribution of energy between SPPs and light channels can be approximately equal to each other, are revealed. In the case of an active system, associated with a magnetic dipole source embedded in a silicon resonator, two separate emission channels into light and into SPPs are considered as well. The radiation efficiency in each channel as a function of the gap is examined and compared. In particular, it is revealed the conditions when the efficiency of resonant light energy propagation along the two channels is practically equal to each other, and the Purcell factor achieves the value almost two times higher than for the case without the substrate. The obtained results elucidate the features introduced by the Mie dipole resonances of silicon nanospheres to control the light scattering (radiation) and the SPP excitation in dielectric/metal interface systems. The results obtained are perspectives for the development of new compact photonic and plasmonic devices operating at standard telecommunication wavelength ranges.