Space-variant polarization conversion with hollow waveguide arrays

We demonstrate the realization of a polarization converter by using an array of rectangular openings in a metallic film. These openings act as array of hollow waveguides. By suitable orientation of the individual openings, a spatially variant polarization conversion can be achieved. As it is known from microwave theory, hollow waveguides have sub-wavelength dimensions in the transverse direction. Thus, for optical wavelengths, the openings have nanometer dimensions. The thickness of the metallic layer (in other words: the propagation length) in our case is several wavelengths. To fabricate the elements and to meet the structural requirements, direct-writing electron beam lithography was used, followed by electroplating with gold. Here, we show results from polarization experiments and compare them with predictions from numerical simulations, where a very good agreement was found.