Exciting surface plasmons with transformation media

TL;DR

This paper introduces a transformation optics-based flat slab device that efficiently excites surface plasmon polaritons without reflections, offering a compact, integrable solution with tunable angular response for plasmonic applications.

Contribution

It presents a novel flat squeezing slab design using transformation optics to excite surface plasmons without reflections, enhancing integration and tunability.

Findings

Enables evanescent coupling to surface plasmons without input reflections

Design achieves a 2.5 times wider angular bandwidth than conventional couplers

Proposes a feasible dielectric implementation for practical use

Abstract

We present a way of exciting surface plasmon polaritons along non-patterned metallic surfaces by means of a flat squeezing slab designed with transformation optics. The slab changes the dispersion relation of incident light, enabling evanescent coupling to propagating surface plasmons. Unlike prism couplers, the proposed device does not introduce reflections at its input interface. Moreover, its compact geometry is suitable for integration. A feasible dielectric implementation of the coupler is suggested. Finally, we show that the angular response of the device can be engineered by using a non-uniform compression factor. As an example, we design a coupler with a half-power angular bandwidth 2.5 times higher than that of a conventional dielectric coupler.