Efficiency of local surface plasmon polariton excitation on ridges

The issue of efficient local coupling of light into surface plasmon polariton (SPP) modes is an important concern in miniaturization of plasmonic components. Here we present experimental and numerical investigations of efficiency of local SPP excitation on gold ridges of rectangular profile positioned on a gold film. The excitation is accomplished by illuminating the metal surface normally with a focused laser beam. Wavelength dependence and dependence of the efficiency on geometrical parameters of ridges are examined. Using leakage radiation microscopy, the efficiency of similar to 20% is demonstrated experimentally. Numerical simulations based on Green's tensor approach are in good agreement with the experiment and allow suggesting an optimization of parameters for improving the efficiency of SPP excitation.