Modeling of Gaussian beam diffraction from a thick single-slit perfectly conducting screen: finite-difference time-domain method vs. rigorous theory

We model the diffraction of incident beams with Gaussian and constant spatial profiles on a thick single-slit perfectly conducting screen. Slit sizes larger and smaller than the wavelength are considered. We calculate the diffraction patterns using the finite-difference time-domain method and compare the results to those obtained by rigorous theory. The results are in good agreement in both cases.