Analysis of binary diffraction gratings: Comparison of different approaches

Abstract

Diffraction characteristics of periodic binary diffractive structures are studied using three different theoretical approaches. Namely rigorous coupled-wave analysis (RCWA), Kogelnik's two-wave method, and the scalar method of transmittance have been applied to study diffraction characteristics and have been compared, and their applicability has been determined. For comparison purposes, a binary surface-relief grating made from an isotropic non-absorbing substrate in the planar diffraction regime, and a transverse electric polarized incident wave, are considered in this paper. Additionally, by calculating the diffraction efficiency of such gratings using the RCWA method, with special respect to grating profile depth and period, it was possible to describe and explain the complex behaviour of diffraction efficiency, that is to find regions with typical diffraction regimes, of all gratings of a chosen kind, in this case given by the binary grating profile. Moreover, it has been shown how the classical scalar transmittance method for analysis of thin diffraction gratings can be modified by an estimation of the propagation process through the grating depth in order to describe the volume phase synchronism dependence on the relative grating period.