Radial beam by amplitude modulation and phase-shifting per quadrant in a double-aperture common-path interferometer

Abstract

In this work, we propose a very simple, and efficient interferometric setup for transforming a homogeneous linearly polarized beam into a radially polarized beam. The proposal is based in a double-aperture common-path interferometer adapted for phase-shifting of π radians per quadrant. It is carried out by placing two composed grating in each aperture, which are built by joining two gratings displaced by a half-period, on horizontal and vertical direction, respectively. The input optical beams are orthogonal and linearly polarized, and their amplitudes are modulated in quadrature. We show that the combination of amplitude-only filters and the π phase-shifting per quadrant can achieve the implementation of complex filters such as the sinusoidal ones. The combination of the spatial modulation of both amplitude and phase generates an optical field with radial polarization. Specialized optical elements of high cost and SLM devices are avoided. We show the theoretical model and experimental results.