The traditional frequency selective surface (FSS) needs further improvement with the development of stealth technology, and the design of multifunctional FSSs is essential. In this letter, an active absorptive FSS (AFSS) has been designed based on the absorption structure of the spoof surface plasmon polariton (SSPP) and the switching activity of the active FSS. The active FSS embedded with PIN diodes realizes the shift of two transmission/reflection frequency bands by controlling the bias voltage of the feed network, which switches from one band-pass response (at around 3.06 GHz) to the other (at around 4.34 GHz). And when one of the transmission windows switches to the other, the original transmission window closes. The upper plasmonic structure achieves a continuous and efficient absorption band from 6.31 to 8.34 GHz. A sample was also fabricated and carried out to verify the numerical simulation, and the experimental and simulation results are consistent. This work provides new ideas for the design of active AFSS and promotes its application in common aperture radome, antenna isolation, and electromagnetic shielding.

No abstract

Tailoring the phase and amplitude of electromagnetic waves has drawn great attention in the microwave, terahertz, and even optics domains. However, the existing method for simultaneous control of these two essential properties suffers from inadequate efficiency and narrow bandwidth, especially for microwave devices. Here, a strategy of overcoming this difficulty is proposed by introducing the ohmic sheet into a Fabry–Pérot‐like cavity. The arbitrary phase modulation can be realized by changing the geometric parameters and the orientation of elliptical split resonance ring; via changing the intensity of ohmic dissipation, the amplitude can be continuously adjusted from 0 to 1. Its most significant advantage is arbitrary wide‐band complex‐amplitude modulation without introducing cross‐polarization crosstalk and backward scattering field interference. To verify its feasibility, three phase‐amplitude holographic imaging ​prototypes at 12, 14, and 16 GHz are designed. Both the simulated and measured results manifest the excellent performances of the proposed metasurface, demonstrating the excellent performances with a remarkable signal‐to‐noise ratio and low root‐mean‐square error. This proposed strategy provides an alternative method to control the phase and amplitude arbitrarily, which not only realizes high‐quality holography but also paves a way for random beamforming and so on.

Multidimensionally (amplitude, polarization, and phase) manipulated metasurfaces have drawn more significant advantages in modern photonic applications. In this paper, the active multidimensionally manipulated metasurface merging Pancharatnam–Berry phase and dynamic phase is proposed. The phase and polarization of the coding elements here can be adjusted dynamically by utilizing positive‐intrinsic‐negative (PIN) diodes. More remarkably, the independent feeding of the coding elements in two layers is creatively proposed so that each coding element of the active coding metasurface (ACM) has four basic response states. And the four states can be dynamically switched by regulating the bias voltages imposed on the PIN diodes through field programmable gate array (FPGA). Therefore, the versatile functionalities of the ACM are achieved and all the functionalities can be implemented in real‐time. As a proof of concept, three specific functionalities are validated both from the simulation and measurement on a fabricated prototype with good coincidence with each other. The ACM can achieve copolarization, crosspolarization anomalous reflection, and circular‐linear polarization conversion for the incident circularly polarized wave. The proposed ACM opens new vistas in active metadevices and has broad application prospects in multifunctional devices and communication systems.

Integrating active and passive manipulation of electromagnetic (EM) waves has significant advantages for the caliber synthesis of microwave and optical integrated devices. In previous schemes, most reported designs focus only on active ways of manipulating self-radiating EM waves, such as antennas and lasers, or passive ways of manipulating external incident EM waves, such as lenses and photonic crystals. Here, we proposed a paradigm that integrates active and passive manipulation of EM waves in a reconfigurable way. As demonstrated, circularly polarized, linearly polarized, and elliptically polarized waves with customized beams are achieved in passive operation by merging Pancharatnam−Berry phases and dynamic phases, while the radiating EM waves with a customized gain are achieved by coupling the coding elements with the radiation structure in the active manipulation. Either active or passive manipulation is determined by the sensed signals and operating state to reduce detectability. Encouragingly, the proposed strategy will excite new sensing and communication opportunities, enabling advanced conceptions for next-generation compact EM devices.