We propose a new design of optical nanoantennas and numerically study their optical properties. The nanoantennas are composed of two cylindrical metal nanorods stacked vertically with a circular dielectric disk spacer. Simulation results show that when the dielectric disk is less than 5nm in thickness, such nanoantennas exhibit two types of resonances: one corresponding to antenna resonance, the other corresponding to cavity resonances. The antenna resonance generates a peak in scattering spectra, while the cavity resonances lead to multiple dips in the scattering spectra. The cavity resonant frequency can be tuned by varying the size of the dielectric disk. The local field enhancement inside the cavity is maximized when the diameter of the dielectric disk is roughly half that of the rod and when the cavity and antenna resonant frequencies coincide with each other. This new nanoantenna promises applications in single molecule surface enhanced Raman spectroscopy (SERS) owing to its high local field enhancements and large scale manufacturability. (c) 2008 Optical Society of America.
This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.16.010315. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Joshi, Bhuwan P.; Wei, Qi-Huo (2008). Cavity Resonances of Metal-Dielectric-Metal Nanoantennas. Optics Express 16(14) 10315-10322. doi: 10.1364/OE.16.010315. Retrieved from https://oaks.kent.edu/cpippubs/368