Experimental evidence of efficient cavity modes excitation in metallic gratings by attenuated total reflection

We provide experimental evidence of an improved excitation of the cavity modes of deep lamellar metallic gratings by using an attenuated total reflection configuration. The reflectivity of gold gratings composed of 1-μm deep channels, with width of 0.7μm, periodically separated by a distance of 1.75μm was measured in the 1000–5000-cm−1 spectral range for several angles of incidence. The spectral width of the resonance excited in this configuration is reduced by a factor of 6 compared with the external reflectivity case, and the field enhancement inside the grooves can reach two orders of magnitude with respect to the incident intensity.