Abstract
Currently, cylindrical beams with radial or azimuthal polarization are being used successfully for the optical manipulation of micro- and nano-particles as well as in microscopy, lithography, nonlinear optics, materials processing, and telecommunication applications. The creation of these laser beams is carried out using segmented polarizing plates, subwavelength gratings, interference, or light modulators. Here, we demonstrate the conversion of cylindrically polarized laser beams from a radial to an azimuthal polarization, or vice versa, by introducing a higher-order vortex phase singularity. To simultaneously generate several vortex phase singularities of different orders, we utilized a multi-order diffractive optical element. Both the theoretical and the experimental results regarding the radiation transmitted through the diffractive optical element show that increasing the order of the phase singularity leads to more efficient conversation of the polarization from radial to azimuthal. This demonstrates a close connection between the polarization and phase states of electromagnetic beams, which has important implications in many optical experiments.
Highlights
Phase singularities of a scalar field, which include vortex phases and phase jumps, are important features of various types of waves[1, 2]
We conducted a theoretical analysis of the effect of sharply focusing a cylindrically polarized beam in the presence of an optical element with a vortex phase
We demonstrated the conversion of polarization state in cylindrically polarized laser beams by introducing a higher-order vortex phase singularity
Summary
Phase singularities of a scalar field, which include vortex phases and phase jumps, are important features of various types of waves[1, 2]. Polarized optical beams, which may have a radial or azimuthal polarization, have attracted the most attention from researchers because of their special properties[12]. In some applications, such as STED (Stimulated Emission Depletion Microscopy) methods[20], it is important to use a specific combination of laser beam polarization and spatial properties. We demonstrate the conversion of polarization type in a cylindrically polarized laser beam by introducing a higher-order vortex phase singularity. The effects of a higher-order vortex phase in a cylindrical vector beam have not been previously studied. A numerical study was performed, and the experimental results fully confirmed the theoretical predictions
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