An Efficient Large-Area Grating Coupler for Surface Plasmon Polaritons

TL;DR

This paper presents a novel grating coupler design that significantly improves the efficiency of coupling visible and near-infrared light into surface plasmon polaritons on a flat metal surface, achieving over 45% conversion efficiency.

Contribution

The authors introduce a highly efficient large-area grating coupler for SPPs, optimized through precise fabrication to meet critical coupling conditions, surpassing previous performance benchmarks.

Findings

Achieved >45% PW-to-SPP power conversion at 780 nm.

Demonstrated that matching SPP losses to coupling strength enhances efficiency.

Fabricated the grating using focused ion beam for precise control.

Abstract

We report the design, fabrication and characterization of a periodic grating of shallow rectangular grooves in a metallic film with the goal of maximizing the coupling efficiency of an extended plane wave (PW) of visible or near-infrared light into a single surface plasmon polariton (SPP) mode on a flat metal surface. A PW-to-SPP power conversion factor > 45 % is demonstrated at a wavelength of 780 nm, which exceeds by an order of magnitude the experimental performance of SPP grating couplers reported to date at any wavelength. Conversion efficiency is maximized by matching the dissipative SPP losses along the grating surface to the local coupling strength. This critical coupling condition is experimentally achieved by tailoring the groove depth and width using a focused ion beam.