Deep metallic surface relief diffraction gratings are shown to couple radiation to surface plasmon polaritons when transverse magnetic radiation is incident in a plane orthogonal to the grating wave vector. This sharp resonance for a deep sinusoidal surface profile is explored using modeling programs and its presence is confirmed experimentally for a silver grating in the visible part of the spectrum.

• Received 20 March 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.3978