Broadside Excitation of Long-Range Surface Plasmons via Grating Coupling

A metal grating for coupling a Gaussian beam incident from broadside to the long-range surface plasmon-polariton (LRSPP) propagating along a membrane-supported Au slab is proposed and modelled by the finite-difference time-domain method. A short grating design consisting of a small number of Au bumps yields a 19.5% coupling efficiency at ¿
₀
= 1310 nm into the LRSPP propagating in a single direction when the grating is excited off-center near one of its edges. The grating coupler is easy to fabricate and it facilitates experimental alignments.