The Thin Element Approximation (TEA) is a widely-used method in e.g. Fourier optics to calculate the diffraction efficiency of gratings. It is however also known that the approximation becomes inaccurate for relatively small grating period. In this example, two types of transmission gratings are selected: sinusoidal and blazed. We use both TEA and FMM (also known as RWCA, which is rigorous) to analyze such gratings with varying period, and by comparing the results, we investigate the behaviors of the two methods.
