Lamellar metallic grating anomalies.

A detailed numerical investigation of anomalies in lossy metallic lamellar gratings is presented in a large interval of a wavelength-to-period λ/d ratio. A substantial increase in absorption (a decrease in the total diffracted energy) is observed. If λ/d is small enough (within the homogenized limit), the absorption can reach almost 100%. When the groove width is large enough, the anomalies are connected with mode resonances inside the grooves.