The field enhancement and optical sensing in the array of almost adjoining metal and dielectric nanorods

The surface plasmon (SP) excitations in the periodical array of the nanorods have attracted a lot of attention in the recent years due to the numerous potential applications in nanoplasmonics including transmitting and processing optical signals on a scale much smaller than the wavelength. In our work the plasmonic and dielectric systems consisting of twodimensional periodic arrays of nanorods are considered. We use computer simulation as well as exact analytical solution to find reflectance and transmittance the plane array of the nanorods, which have various diameters and inter-particle spacing. As the metal nanorods approach each other, series of surface plasmon resonances are excited. The resonances are strongly localized between nanorods due to its collective nature. It is shown that the local electric field is much enhanced in the interparticle gap and it concentrates at a scale much smaller than the diameter of the rod. The reflectance and transmittance have sharp minima and maxima corresponding to the excitation of various SP resonances. The computer simulations are in an agreement with our analytical theory. In the case of the dielectric nanorods the phenomenon of the whispering gallery modes effect is considered. The resonance frequencies and field enhancement can be tuned by variation of the shape and arrangement of the nanorods. The system of nanorods that almost touched each other by their generatrices can be used to develop plasmon and dielectric substrates, which are the basic elements of high sensitive SERS bio and chemical sensors.