Polarisation conversion at a textured surface

It has previously been shown that the electric vector of visible-wavelength radiation can be rotated through 90° by reflecting photons from a suitably aligned diffraction grating. The phenomenon has now been directly extended to the microwave regime, and the use of gratings exhibiting a finite number of grooves has been investigated. While efficient conversion has been obtained from gratings consisting of as few as five grooves, the wavelength dependence of the effect is not in good agreement with an unmodified optical model of the system. Several possible explanations were investigated, and it was deduced that the main error was due to the nonplanar wavefronts produced by the source. An experimental solution to this problem is suggested