Electromagnetic response of novel high refractive index dielectric structures in nematic liquid crystal medium. IT. 11

Sub-wavelength periodic metallic nanostructures give rise to very interesting optical phenomena like effective refractive index, perfect absorption, cloaking, etc. However, such metallic structures result in high dissipative losses and hence dielectric nanostructures are being considered increasingly to be an efficient alternative to plasmonic materials. High refractive index (RI) dielectric nanostructures exhibit magnetic and electric resonances simultaneously giving rise to interesting properties like perfect magnetic mirrors, perfect absorbers, etc. In the present work, we study light-matter interaction of novel geometric dielectric structures such as cubes and pentagonal prisms made of very high refractive index material Te in air. We observe a distinct band-like structure in both transmission and reflection spectra resulting from the near-field coupling of the field modes from neighboring dielectric structures. We investigated the effect of periodicity of the dielectric layer on the resonance characteristics. An earlier unreported sharp resonance is observed at slightly higher frequency to the resonance band for all the periodicities. From the spatial distribution of the electric and magnetic fields and a detailed multipole analysis in both spherical harmonics and Cartesian components the dominant resonant modes are identified to be electric and magnetic dipoles and the sharp peak at higher frequencies is due to excitation of toroidal dipole mode. Effect of asymmetric periodicity and the thickness of the dielectric structures on the resonance characteristics are also studied. (author)