Light diffraction from a metallic bigrating.

The diffraction of $\pi $- and $\sigma $- polarized electromagnetic plane waves from metallic bigratings is studied theoretically. The reduced Rayleigh equations are solved using a perturbation approach. The diffracted amplitudes are calculated until second order on the surface height profile. Numerical results of the diffraction orders and Near-Field are obtained using both, two-dimensional sinusoidal and semicircular profiles.