Design and Experimental Demonstration of Impedance-Matched Circular-Polarization-Selective Surfaces with Spin-Selective Phase Modulations

Abstract

This paper presents the design and experimental demonstration of an impedance-matched circular polarization selective surface which also offers spin-selective phase modulations at microwave frequencies. We achieve this by leveraging the theory of Pancharatnam-Berry phase and cascading four tensor impedance layers, each comprising an array of crossed meander lines. These meander lines are precisely tuned and rotated to implement particular tensor surface impedance values to satisfy the impedance-matching condition for the transmitted right-handed circularly-polarized field while inducing Pancharatnam-Berry phase shift for the reflected left-handed circularly-polarized field. We present a detailed numerical synthesis technique to obtain the required impedance values for satisfying the impedance matching condition, and demonstrate spin-selective phase modulations based on Pancharatnam-Berry phase shifts. To verify the proposed idea, we experimentally demonstrate nearly-reflectionless transmission of right-handed circular polarization at broadside and reflection of left-handed circular polarization at 30 • off broadside at 12 GHz. For this purpose, a free-space quasi-optical set up and a near-field measurement system are respectively employed for measuring the transmitted and reflected circularly-polarized fields.

Microwave Huygens’ Metasurfaces: Fundamentals and Applications

“…On the other hand, in chiral metasurfaces the induced electric (magnetic) currents are parallel to the acting magnetic (electric) fields, meaning that the tensors K em , K me have off-diagonal nonzero elements. This type of bianisotropy is essential to design HMSs for chiral polarization effects, such as polarization rotation or circular polarization selectivity [17]- [19].…”

“…In [19], the idea of cascading anisotropic electric layers for realizing a chiral metasurface was further expanded by also combining wavefront engineering capabilities. In particular, the authors incorporated the theory of Pancharatnam-Berry phase shift in the design of a CPSS to selectively apply a phase shift only for the reflected CP wave, while preserving the impedance-matching condition for the opposite handedness.…”

“…After discretizing the HMS, the response at each unit cell can then be modeled through an impedance matrix Z or a generalized scattering matrix S with their elements given as a function of Z se , Y sm , K em at each sampling point [15], [20]. In other design scenarios, such as chiral HMSs, it may be more convenient to directly define lossless scattering matrices without going through the formulation involving the tensors Z se , Y sm , K em , K me [18], [19]. Lastly, it should be emphasized that the physically realized unit cells inevitably suffer from copper and dielectric losses.…”

Extreme Beam-forming with Impedance Metasurfaces Featuring Embedded Sources and Auxiliary Surface Wave Optimization

“…The strong and efficient interaction between radio frequency electromagnetic waves with metals has led to the development of printed circuit board (PCB) metasurfaces whose constituent meta-atoms are fabricated by etching designed conductive patterns on dielectric substrates. Due to their compact form factor and their unprecedented ability to precisely control various aspects of the electromagnetic waves, such as the phase [8]- [11], amplitude [12], polarization [13]- [15] and frequency content [16], [17], PCB MTSs represent the ideal platform for realizing the next generation of antennas. They have already been successfully integrated into existing technologies such as transmitarray [18], [19] and reflectarray [20], [21] antennas.…”

Systematic Design of Transmission-Type Polarization Converters Comprising Multilayered Anisotropic Metasurfaces

“…Several examples of polarization converters based on Frequency Selective Surfaces (FSS) and metasurfaces have been proposed in the literature [3][4][5][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Some of the available configurations are designed at a single frequency [3][4][5][18][19][20][21][22][23][24]. On the other hand, other configurations available in the literature are instead capable of converting the polarization over a broad frequency band [5,[25][26][27][28][29][30].…”