Highly Efficient Excitation of Surface Plasmon Polaritons Under Asymmetric Dielectric Surroundings

We demonstrate a single deep subwavelength slit for efficiently improving the excitation of surface plasmon polaritons (SPP) on metals through raising the dielectric permittivity of the output surrounding medium and numerically investigating their physical properties. Via adjusting the slit width and the output permittivity, either SPP launching intensity or its efficiency can be enhanced by almost 25 times and 170 %, respectively, compared with that under the symmetric surroundings. The underlying mechanisms are attributed to the spatial distribution change of the transmitted field and the plasmon density of state (DOS).