Waveguide Grating Radial Polarizer for the Photolithography of Circularly Symmetrical Optical Elements

A radially periodic slab waveguide grating of concentric circular lines composed of a corrugated quartz substrate and a ZnS waveguiding layer under the condition of normal incidence $ \hbox{TE}_{0}$ mode coupling at the 442-nm wavelength of a circularly polarized HeCd laser exposure beam causes a close to 100% reflection of the local TE polarization and a high transmission of the local TM polarization, thus transmitting a radially polarized beam. The functionality demonstration is first made with a grating written by e-beam; then, the same element is obtained by means of a phase-mask projection with radial spatial frequency doubling with the first element used as a radial polarizer.