Coupling of waveguide and surface modes in enhanced transmission through stacking gratings

The physics of enhanced transmission through two metallic gratings stacked one on top of another with a lateral shift is studied. Full electromagnetic calculations via the method of rigorous coupled-wave analysis show that enhanced transmission may result even when the slits in one grating are covered by the other. Despite the channel of waveguide mode is blocked, the coupling of strongly excited surface modes in one grating to the waveguide mode in another leads to an enhanced transmission which could even be larger than that in the case of two stacking gratings unshifted with respect to one another. (c) 2006 American Institute of Physics.