Abstract
Theoretical demonstration of efficient coupling and power concentration of radially-polarized light on a conical tip of plasmonic needle is presented. The metallic needle is grown at the center of radial plasmonic grating, engraved in a metal surface. The electromagnetic field distribution was evaluated by Finite Elements and Finite-Difference-Time-Domain methods. The results show that the field on the tip of the needle is significantly enhanced compared to the field impinging on the grating. The power enhancement exhibited a resonant behavior as a function of needle length and reached values of approximately 10(4). Test samples for few types of characterization schemes were fabricated.
Highlights
Fast development of nano-scale technology enables the examination of basic phenomena in physics, biology and chemistry, and allows a variety of implementations and applications
The integrated power flow includes that of the needle Surface Plasmons Polaritons (SPPs) and the corresponding upward part of the vortex flow, centered at the position approximately indicated by the white arrows
This resonance can be illustrated by varying the plasmonic needle height and measuring Ez field enhancement at the conical tip (Er = 0 there), relative to the field in the center of the gratings structure with no needle
Summary
Fast development of nano-scale technology enables the examination of basic phenomena in physics, biology and chemistry, and allows a variety of implementations and applications. It was shown recently that plasmonic assisted focusing is much more efficient if the impinging light is radially polarized - better matching both the circular symmetry of the structure and the plasmon polarization In addition it allows for constructive interference of the dominant out-of-plane electric field component at the center of the structure [16,17, and 18,]. A variety of device parameters were shown to be controlled: needle height and diameter (Fig. 1(b)), gratings period and modulation depth which are promising results for ongoing experiments The excitation of such high field intensities (hot spots) is important for validating basic limiting factors of plasmonic power concentration (e.g. nonlocal effects [21]), efficient near field inspection and writing (nanolithography, memories), and efficient coupling of nano emitters/absorbers to the far field. The dependence of the plasmonic modes on the excitation polarization was investigated
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