NUMERICAL ANALYSIS OF SCATTERING FROM ECHELETTE GRATING - SMOOTHING PROCESS ON MODE-MATCHING METHOD.

The mode matching method is a general numerical technique to solve problems of electromagnetic fields. This method is, however, unable to derive an accurate approximate solution for Neumann boundary value problems of a complex scattering body. This paper attempts to remove such drawbacks by introducing a smoothing procedure in which the modal expansion is matched with boundary conditons via an indefinite integral. The problem of scattering from an echelette grating is solved by the conventional mode matching method and the new smoothing procedure. Numerical results indicate that the error of the approximate solution obtained by the new method is only about one tenth compared to the conventional procedure. Numerical examples for power distributions of scattered waves versus the incident angle and the wavenumber of incident plane waves are given.