Using a phenomenological theory of diffraction gratings made by perturbing a planar waveguide allows us to deduce important properties of the sharp filtering phenomena generated by this kind of structure when the incident light excites a guided wave. It is shown that the resonance phenomenon occurring in these conditions acts on one of the two eigenvalues of the Hermitian reflection matrix only. As a consequence, we deduce a mathematical expression of the reflectivity and demonstrate that high-efficiency filtering of unpolarized light requires the simultaneous excitation of two uncoupled guided waves. Numerical examples are given.
© 2002 Optical Society of America
(060.1810) Fiber optics and optical communications : Buffers, couplers, routers, switches, and multiplexers
(060.4230) Fiber optics and optical communications : Multiplexing
(230.1950) Optical devices : Diffraction gratings
(230.5440) Optical devices : Polarization-selective devices
(230.7400) Optical devices : Waveguides, slab
Anne-Laure Fehrembach, Daniel Maystre, and Anne Sentenac, "Phenomenological theory of filtering by resonant dielectric gratings," J. Opt. Soc. Am. A 19, 1136-1144 (2002)