DISPERSION OF SURFACE-PLASMONS IN RECTANGULAR, SINUSOIDAL, AND INCOHERENT SILVER GRATINGS

The dispersion behavior of surface plasmons on silver gratings in the center of the first Brillouin zone is determined by measurements of the reflected light as a function of amplitude and of the profile of the gratings. We studied the dispersion relation of sinusoidal gratings, rectangular gratings, and incoherent gratings. We found a strict relationship between the profile of the grating and the dispersion relation of the surface plasmons. Our experiments showed at small amplitudes a crossing of the dispersion branches without a gap. For higher amplitudes a frequency or a momentum gap occurred depending on whether the profile had higher Fourier components or not. The experimental results are in accordance with numerical simulations.