Nanooptics and nanophotonics
Polarization degree of freedom for guided waves
Yermakov O.1, Polevoy S.2
1 Department of Computer Physics, V. N. Karazin Kharkiv National University, 61022, 4 Svobody Square, Kharkiv, Ukraine.
E-mail: oe.yermakov@gmail.com 

2 Radiospectroscopy Department, O.Ya. Usikov Institute for Radiophysics and Electronics NASU, 61085, 12 Acad. Proskury Str., Kharkiv, Ukraine.

The spectrum of electromagnetic plane waves in any isotropic homogeneous medium is twice degenerate with respect to polarization at any frequency and in any direction, because the dispersions of TE- and TM-polarized eigenmodes are absolutely the same. The operational principle of any bulk classical polarizer is based on the removal of the polarization degeneracy by using an anisotropic slab. Miniaturization and planar technologies lead to the high localization of the electromagnetic signal in the plane of propagation. However, at the same time, the degeneracy is removed. So, there is no polarization degree of freedom for planar photonic devices with in-plane electromagnetic wave propagation. It significantly limits the functionality of flat optical and planar photonic devices. 
In this work, we aim merging the polarization degeneracy and high localization for guided waves propagating within an all-dielectric metasurface. Namely, we theoretically study the periodic subwavelength array of cylinders with high refractive index and demonstrate the broadband TE-TM polarization degeneracy of its guided modes. This concept can be transferred to the optical and infrared ranges using other material platforms and opens new opportunities for the polarization control of guided waves such as metasurface-based waveguide polarizer [1]. These results could potentially become a platform for new generation of planar photonic polarization devices.
S.P. acknowledges the financial support from the project “All-dielectric metasurfaces with polarization-degenerate spectrum for high-precision angle-resolved chiral sensing” (Agreement 05/01-2022(4) on 01.03.2022 between the NAS of Ukraine and the IRE of the NAS of Ukraine). O.Y. acknowledges the financial support within the grant topic #1-46-22 "Interaction of quasiparticles with nanostructures surfaces of arbitrary degree of roughness" with the basic funding by the Ministry of Education and Science of Ukraine.

1.	Yermakov O. Y., Bogdanov A. A., Lavrinenko A. V. Broadband polarization degeneracy of guided waves in subwavelength structured ZnO pattern // IEEE J. Sel. Top. Quant. El. – 2019. – 25. – №. 3. – P. 1-7.