Modal analysis of lamellar gratings using the moment method with subsectional basis and adaptive spatial resolution

We formulate the problem of diffraction by a one-dimensional lamellar grating as an eigenvalue problem in which adaptive spatial resolution is introduced thanks to a new coordinate system that takes into account the permittivity profile function. We use the moment method with triangle functions as expansion functions and pulses as test functions. Our method is successfully compared with the Fourier modal method and the frequency domain finite difference method.