Polarization-Insensitive Metalens and Its Applications to Reflectarrays With Polarization Diversity

A synthesized strategy for achieving polarization-insensitive metalens is proposed by imposing identical parabolic phase patterns individually on two decoupled left-handed (spin up,
$\sigma +$
) and right-handed (spin down,
$\sigma -$
) circular polarization (CP) channels of an anisotropic scheme. This is enabled by synergizing dynamic phases and local geometric phases within 0° and 90° rotations. As a consequence, similar focusing behavior is expected when it is illuminated by a plane wave of arbitrary polarization since any incoming wave is a superposition of
$\sigma +$
and
$\sigma -$
wave. Such an intriguing feature can be utilized to engineer a polarization-insensitive reflectarray/transmitarray in a shared aperture by placing a feeding source of different polarizations at its focal spot without altering the array aperture. Therein, the polarization of the meta-array is determined by its feeding which is readily to be changed in practice. For demonstration and possible applications, two reflectarrays composed of
$50\times50$
elements at Ku band with one in normal and the other in offset configuration were designed and experimentally characterized. Numerical and experimental results illustrate that both reflectarrays are able to work in Dual linear polarization (LP) and Dual CP states by utilizing LP and CP horns of different orientations. Moreover, the versatile polarization-agile property does not pose a significant penalty on its radiation performance and both reflectarrays exhibit a measured peak aperture efficiency of 63.8% and 39.6%, respectively, near 14 GHz, and a 1 dB gain bandwidth more than 11.8%.