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

TL;DR

This paper investigates giant reflection bands and negative transmission in a dielectric grating slab, revealing complex interference effects and potential applications in planar cavity design through an exact analytical approach.

Contribution

It provides an exact analytical study of optical effects in dielectric gratings, highlighting the interplay of waves responsible for giant reflection and negative transmission.

Findings

Giant reflection band arises from complex wave interactions.

Negative transmission occurs under specific incidence conditions.

Comparison with homogeneous slabs clarifies the origin of anomalies.

Abstract

The fundamental optical effects that are at basis of 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 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 of the well known broad reflection bands in high contrast dielectric grating slab in the sub-wavelength regime, obtained by the destructive interference between the travelling 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, as well as among the travelling fundamental wave and the first quasi-guided diffracted one, also among the higher in-plane wave- vector components of the evanescent/divergent waves. To better describe this effect we will compare the optical response of the self-sustained high contrast dielectric grating slab with a system composed by 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 second kind Wood's anomalies generation. Finally, the electromagnetic field confinement in a patterned planar cavity, where the mirrors are two self-sustained rectangular dielectric grating slabs, is briefly discussed.