A Numerical Analysis of Plane-Wave Diffraction from a Multicoated Grating.

In this paper, a numerical analysis algorithm has been derived for the analysis of the problem of plane wave diffraction by a multilayered grating. This algorithm is based on the Yasuura method with the smoothing procedure and can be applied to the problems of arbitrary multilayered dielectric (or metallic) grating with smoothly shaped grooves. The convergence of the approximate solution obtained by the present algorithm has been investigated numerically. It was demonstrated that a highly accurate approximate solution can be computed by the introduction of the smoothing procedure. The present algorithm is applicable to problems of a multilayered grating over the range from infrared to visible. As a numerical example, the diffraction efficiency of the multilayered diffraction grating made of alternate lamination of the high-index and low-index dielectric layers deposited on a metal grating is calculated by the algorithm in this paper. The following items are confirmed: (1) by coating dielectric films, the power absorption of the incident light by the metal grating is reduced in a specific wavelength region; and (2) in a multilayered grating, anomalous resonant absorption occurs by the coupling of the guided mode excited by the dielectric thin film and the diffracted wave. [ABSTRACT FROM AUTHOR]