Bifocal Fresnel lens based on the polarization-sensitive metasurface

TL;DR

This paper introduces a polarization-sensitive Fresnel lens using a metasurface that can focus different polarizations to separate spots, demonstrated at GHz frequencies, with potential extension to THz and visible spectra.

Contribution

A novel metasurface-based bifocal Fresnel lens that separates focal spots by polarization, enabling dynamic control and multiplexing in electromagnetic wave manipulation.

Findings

Successfully demonstrated polarization-dependent focusing at GHz frequencies.

Achieved wavelength-separated focal spots with low crosstalk.

Potential for extension to THz and visible spectral ranges.

Abstract

Thin structured surfaces allow flexible control over propagation of electromagnetic waves. Focusing and polarization state analysis are among functions, required for effective manipulation of radiation. Here a polarization sensitive Fresnel zone plate lens is proposed and experimentally demonstrated for GHz spectral range. Two spatially separated focal spots for orthogonal polarizations are obtained by designing metasurface pattern, made of overlapping tightly packed cross and rod shaped antennas with a strong polarization selectivity. Optimized subwavelength pattern allows multiplexing two different lenses with low polarization crosstalk on the same substrate and provides a control over focal spots of the lens only by changing of the polarization state of the incident wave. More than a wavelength separation between the focal spots was demonstrated for a broad spectral range, covering half a decade in frequency. The proposed concept could be straightforwardly extended for THz and visible spectra, where polarization-sensitive elements utilize localized plasmon resonance phenomenon.