Coupled-wave analysis of reflection gratings

Diffraction of electromagnetic waves by longitudinally periodic media (reflection gratings) is rigorously analyzed using an exact coupled-wave approach. The analysis is formulated in a simple matrix form easily implemented on a digital computer. The intensities of the two waves, the diffracted (reflected) and transmitted waves, are calculated for a wide range of parameters. These exact results are then compared to results obtained with approximate two-wave modal, and with multiwave and two-wave coupled-wave analyses. The applicability of these approximate theories is discussed. The case of other than first-order Bragg incidence is also included.