Broadband polarization degeneracy of guided waves in subwavelength structured ZnO pattern

Polarization degeneracy of electromagnetic plane waves in vacuum and in any bulk isotropic media is the keynote operational principle of many optical devices such as polarizers and interferometers. However, surface and guided waves spectra are typically either not degenerated at all or meet degeneracy only at very specific dispersion points. In this work, we offer a design of a periodic photonic structure based on zinc oxide (ZnO) nanocylinders providing the broadband polarization degeneracy of the guided waves in the near-IR frequency range. We analyze the impact of the spatial dispersion and substrate on the degeneracy breaking. We offer the design based on ZnO nanocylinders with aluminum-doped zinc oxide (AZO) substrate, achieving the degeneracy in the vicinity of a telecommunication wavelength, for the practical implementation. Finally, we propose and verify numerically a potentially important device - waveguide polarizer, which is the analogue to the <formula><tex>$\pi$</tex></formula>/4 plate for the guided waves.