Diffraction from highly conducting lamellar gratings in conical mountings

Abstract

The modal method based on a surface impedance approximation is extended to conical mountings valid for highly conducting lamellar gratings. The results of this theory are then compared with those obtained by an exact method which are in good coincidence for highly conducting gratings. It is demonstrated that for highly conducting materials this method yields accurate results while the exact modal method has its numerical limitations. Furthermore, polarization conversion in transmittance has been studied experimentally on gold gratings as well as by numerical calculations. It is then shown that wire gratings can act as effective polarization rotators in a transmitted-light configuration. Moreover, polarization conversion can be utilized to study the excitation of surface polaritons on highly conducting gratings. The dispersion of surface polaritons has been evaluated from transmittance measurements in conical mountings.