Excitation of remarkably nondispersive surface plasmons on a nondiffracting, dual-pitch metal grating

A nondiffracting metallic lamellar grating formed from three equally spaced grooves per repeat period, with one being slightly shallower than the other two is examined at microwave frequencies. When filled with a slightly lossy dielectric, this structure supports a remarkably nondispersive surface plasmon polariton mode, which exhibits strong selective absorption of incident power. Measured reflectivities show excellent agreement with the results predicted by a rigorous coupled wave theory.