We present measurements of enhanced resonant transmission of infrared radiation through subwavelength metallic gratings made of rectangular grooves. This is achieved either by exciting a resonant waveguide mode in the cavities, or when the field is large enough above the groove, which is particulary satisfied close to surface plasmon excitation conditions at the air/metal interface. Moreover, we show that a model with plasmons on the incident side only explains this result very well.

• Received 16 July 2002

DOI:https://doi.org/10.1103/PhysRevB.66.161403