Subwavelength Diffraction Grating with Continuous Ridges for Inverse Energy Flux Generation

In this paper we derive the equations for the subwavelength grating vector of polarization element that creates the second order radially polarized beam. We show that the element can be implemented with different shape for different orientations of the input and output polarization. There can be sun- or mira-shape and axicon shape. Intermediate shape is also possible. Also we conduct numerical simulation of creation and focusing of the second order radially polarized beam. It is shown that the inverse energy flow can arise near the optical axis of the element.