Dynamic control of Bessel beams with longitudinally varying polarization through liquid-crystal anisotropic axicons

In this work we discuss liquid-crystal (LC) anisotropic axicons for the dynamic control of the Bessel beam polarization variation along propagation. We first present a technique that employs a LC spatial light modulator (LC-SLM) to display two diffractive axicons, each one affecting one of the two orthogonal linear polarization components. If the two axicons have a slightly different period, a periodic variation in the polarization state of the Bessel beam occurs over propagation. Second, we present a more compact alternative consisting in a combination of a refractive axicon and a LC element of linear phase profile along the radial coordinate. This combination creates a compound compact and tunable anisotropic axicon that produces Bessel beams with tunable polarization modulation. The capability of changing the polarization state of the Bessel beam along its propagation opens new venues in axial polarimetry, optical trapping in multiple planes or axial-dependent laser microfabrication.