Out of plane mode conversion and manipulation of Surface Plasmon Polariton Waves

M Sathish Kumar,Sunkyu Yu,Xianji Piao,Namkyoo Park,Sukmo Koo

doi:10.1364/oe.18.008800

Abstract

We propose a rigorous design method of structured gratings for out of plane mode conversion, line focusing and manipulation of Surface Plasmon Polariton (SPP) waves. Employing a blazed grating to incorporate the directionality of SPP launch, and at the same time controlling grating depth and chirp to account for the radiation loss and diffraction angle, it was possible to achieve high efficiency and flexible SPP to freespace mode conversion. Devices with advanced functionalities, such as balanced SPP power splitter, and SPP wavelength demultiplexer are demonstrated with over 75% of power efficiencies at reasonable working distances of less than several wavelengths.

Highlights

Surface Plasmon Polariton (SPP), understood as electromagnetic waves formed by charge oscillations at the surface of a metal, have found serious interest among a wide cross section of scientists including physicists, chemists and biologists
Design strategy will be detailed for various functional devices, with numerical confirmation through Finite Element Method (FEM) and Finite Difference Time Domain (FDTD) analysis
Excitation of SPP modes on a metal-dielectric interface, by illuminating a plane wave on a properly designed grating structure carved on the metal surface has been well addressed in the past [4]

Summary

Introduction

Surface Plasmon Polariton (SPP), understood as electromagnetic waves formed by charge oscillations at the surface of a metal, have found serious interest among a wide cross section of scientists including physicists, chemists and biologists. Serious efforts have been made for the focusing of SPP as well, in order to achieve enhanced field intensity at the focal point or to couple to other types of waveguides, utilizing metal-surface engineering or chirped dielectric grating at the exit of plasmonic waveguides [5,6] or through plasmonic nanoantennas [7]. Reports such as [8] which use SPPs in metallic nanoslits with variant widths, to focus light have appeared. Design strategy will be detailed for various functional devices, with numerical confirmation through Finite Element Method (FEM) and Finite Difference Time Domain (FDTD) analysis

Theory and design methodology

Results

Conclusion