ABSTRACT
At the beginning of the last century, Wood [1] showed that when he sends a polarized light on a diffraction grating on metal plate, a very unusual reflected pattern of dark and light bands can be observed. That was the first noticed observation of uncommon attenuated reflection on gratings. A few years later, in 1907, Rayleigh [2] showed theoretically some basic properties of gratings using a plane wave expansion of the scattered electromagnetic field. He found that the scattered field was singular at wavelengths for which one of the spectral orders emerged from the grating at the grazing angle. He then observed that these wavelengths corresponded to the Wood anomalies. Furthermore, these singularities appeared only when the electric field was polarized perpendicular to the grooves. When the magnetic field was perpendicular, there was no anomaly [3]. More explanations were given by Palmer [4] for deep gratings.
