A perfectly matched layer for finite-element calculations of diffraction by metallic surface-relief gratings

We introduce a perfectly matched layer approach for finite element calculations of diffraction by metallic surface-relief gratings. We use a non-integrable absorbing function which allows us to use thin absorbing layers, which reduces the computational time when simulating this type of structure. In addition, we numerically determine the best choice of the absorbing layer parameters and show that they are independent of the wavelength.