Giant reflection band and anomalous negative transmission in a resonant dielectric grating slab: Application to a planar cavity

The fundamental optical effects that are the basis of the giant reflection band and anomalous negative transmission in a self-sustained rectangular dielectric grating slab in p polarization and for incidence angle not very far from the Brewster's angle of the equivalent slab are investigated. Notice that the self-sustained dielectric grating slab is the simplest system that, due to the Bragg diffraction, can show both of the former optical effects. A systematic study of its optical response is performed by an analytical exact solution of the Maxwell equations for a general incidence geometry. At variance with the well-known broad reflection bands in high-contrast dielectric grating slabs in the sub-wavelength regime, obtained by the destructive interference between the traveling fundamental wave and the first diffracted wave (a generalization of the so-called second kind Wood's anomalies), the giant reflection band is a subtle effect due to the interplay among the traveling fundamental wave and the first quasiguided diffracted one, as well as among the higher in-plane wave-vector components of the evanescent/divergent waves. To better describe this effect we compare the optical response of the self-sustained high-contrast dielectric grating slab with a system composed of an equivalent homogeneous slab with a thin rectangular high-contrast dielectric grating engraved in one of the two surfaces, usually taken as a prototype for the generation of second kind Wood's anomalies. Finally, the electromagnetic field confinement in a patterned planar cavity, where the mirrors are two self-sustained rectangular dielectric grating slabs, is briefly discussed.