Hybrid Plasmonic Waveguide Based on Tapered Dielectric Nanoribbon: Excitation and Focusing
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The nanofocusing of light source was proposed and simulated using the dielectric-loaded surface plasmon polariton (SPP) model with various laterally tapered planar dielectric architectures on the top surface of the metal. By using finite-difference time-domain method, enhancement factor for the local electric field under distinctive incident polarization was analyzed with different taper apexes under various incident wavelengths and incident angles of the excitation laser. The SPP dispersion and the effect of dissipation on adiabatic nanofocusing of SPP in a sharp taper structure were used to predict the optimal taper angles of the structure and to explain the phenomena of SPP wave slowing down as it propagating toward the taper end. This SPP nanofocusing process was also experimentally realized by illuminating the structure of a tapered CdS nanoribbon deposited on the Ag surface. As the emission of the focused SPP at the taper end, the proposed plasmonic structure can be severed as a light nanosource emitter in the future optical integrated circuits.