Large magnetic to electric field contrast in azimuthally polarized vortex beams generated by a metasurface (Presentation Recording)

Mehdi Veysi; Caner Guclu; Filippo Capolino

doi:10.1117/12.2188890

5 October 2015 Large magnetic to electric field contrast in azimuthally polarized vortex beams generated by a metasurface (Presentation Recording)

Mehdi Veysi, Caner Guclu, Filippo Capolino

Author Affiliations +

Proceedings Volume 9544, Metamaterials, Metadevices, and Metasystems 2015; 954408 (2015) https://doi.org/10.1117/12.2188890
Event: SPIE Nanoscience + Engineering, 2015, San Diego, California, United States

Abstract

We investigate azimuthally E-polarized vortex beams with enhanced longitudinal magnetic field. Ideally, such beams possess strong longitudinal magnetic field on the beam axis where there is no electric field. First we formulate the electric field vector and the longitudinal magnetic field of an azimuthally E-polarized beam as an interference of right- and left-hand circularly polarized Laguerre Gaussian (LG) beams carrying the orbital angular momentum (OAM) states of -1 and +1, respectively. Then we propose a metasurface design that is capable of converting a linearly polarized Gaussian beam into an azimuthally E-polarized vortex beam with longitudinal magnetic field. The metasurface is composed of a rectangular array of double-layer double split-ring slot elements, though other geometries could be adopted as well. The element is specifically designed to have nearly a 180° transmission phase difference between the two polarization components along two orthogonal axes, similar to the optical axes of a half-wave plate. By locally rotating the optical axes of each metasurface element, the transmission phase profile of the circularly polarized waves over the metasurface can be tailored. Upon focusing of the generated vortex beam through a lens with a numerical aperture of 0.7, a 41-fold enhancement of the magnetic to electric field ratio is achieved on the beam axis with respect to that of a plane wave. Generation of beams with large magnetic field to electric field contrast can find applications in future spectroscopy systems based on magnetic dipole transitions, which are usually much weaker than electric dipole transitions.

Conference Presentation

Citation Download Citation

Mehdi Veysi, Caner Guclu, and Filippo Capolino "Large magnetic to electric field contrast in azimuthally polarized vortex beams generated by a metasurface (Presentation Recording)", Proc. SPIE 9544, Metamaterials, Metadevices, and Metasystems 2015, 954408 (5 October 2015); https://doi.org/10.1117/12.2188890

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