ABSTRACT
Programmable metamaterials are suitable for their dynamic and real-time control capabilities of electromagnetic (EM) functions in radars and antenna communications, but it remains a challenge to achieve dynamic modulation of arbitrary transmission phase with high transmission efficiency. Here, we propose a paradigm to tailor transmission phase shift in real time by switching modes between waveguide and SSPP based on the voltage-driven PIN diodes. Step-like phase shift is achieved by the "ON" and "OFF" states of PIN diodes, while continuous phase regulation is by the characteristic of the nonlinear region between those two states. As validations, three systems with programmable functionalities are implemented, including the multibeam generator, the dual-beam scanner, and the active phased-array antenna. The experimental results are consistent with simulation, which verify the feasibility of the proposed approach. Our work offers an alternative route for transmission full-phase modulation and provides unprecedented potential for high-gain, real-time, and multidimensional EM capabilities in applications such as active phased array radars, self-adaption radomes, smart beam shaping.
ABSTRACT
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.
ABSTRACT
Polarization, as an important property of light, has been widely discussed in modern detecting and radar systems. A polarization converter that can be used to achieve dynamic control is regarded as an excellent alternative for implementing the integrated functionalities of communication and stealth. In this work, we propose a paradigm of meta-converter for dynamic polarization states shifting from linear-to-linear (LTL) to linear-to-circular (LTC) polarization. The strategy is achieved by loading voltage-controlled PIN diodes on the double-arrows metallic meta-resonators. The operation modes can be switched by changing the bias voltage. When the PIN diodes are turned on, the polarization meta-converter (PMC) will reflect and convert a linearly polarized electromagnetic (EM) wave into a circularly polarized one in 5.6-15.5 GHz with an axial ratio (AR) below 3dB. When the PIN diodes are turned off, the PMC will reflect and convert a linearly polarized EM wave into the orthogonal counterpart in 7.6-15.5 GHz with a polarization conversion ratio (PCR) over 88%. Simulations and experimental results show a good agreement, which manifests the feasibility of our proposed meta-converter. Moreover, the proposed PMC has great potential for polarization-dependent communication and stealth systems.
ABSTRACT
Integrating diversified functionalities within a single aperture is crucial for microwave and optics-integrated devices. To date, research on this issue suffers from restricted bifunctionality, inadequate efficiency, and the limitation of extending to manipulate full-space wave. Here, we propose a general paradigm to achieve full-space multifunctional integration via tailoring the excited and cutoff states of spoof surface plasmon polaritons (SSPPs). A plasmonic meta-atom consisting of judiciously arranged metallic strips is used to excite and cut off the SSPP mode with uniaxially anisotropic characteristics. By shaping the topological structure of the meta-atom, the transmission and reflection phases are arbitrarily controlled at each pixel. Accordingly, the cross-placed meta-atom arrays can be designed to achieve independent phase profiles for x-/y-polarized transmission/reflection waves through dispersion engineering. A metamaterial with quadruple functionalities of backward beams scattering/anomalous reflection and electromagnetic transmission focusing/vortex is designed and fabricated as a proof-of-principle to reveal flexible manipulation. Both simulation and experimental verification are carried out in microwave frequency to demonstrate the feasibility.
ABSTRACT
Owing to the intriguing capability of manipulating electromagnetic (EM) properties, the metasurface has aroused great attention of researchers and promoted its applications in EM invisibility. However, there are strong demands to provide an efficient transparent window for signals transmitting in EM invisibility devices. Here, we propose a scheme of a circular dichroism assisted metadevice to provide efficient transmission and broadband absorption in microwave frequencies. By employing chiral meta-atoms to introduce a strong asymmetric response for circularly polarized waves, a chiral metadevice for spin-selective absorption with an efficient transmission is presented. Then, we couple four chiral atoms into a polarization-insensitive atom pair, thus the achiral metadevice presents an identical high-efficiency absorption for both the x- and y-polarized wave. Here, both the chiral and achiral metadevices are realized by loading the metasurface-based absorber on a bandpass frequency selective surface. A proof-of-prototype is fabricated to verify the achiral design. The simulated and experimental results have demonstrated wideband, high-efficiency, polarization-insensitive absorption and high in-band transmission. Interestingly, the proposed paradigm can not only provide the potential for chirality-enhanced absorber design but also may trigger applications in spin-dependent systems, stealth antenna systems, and EM camouflage devices.
ABSTRACT
Equipped with the capability of simultaneous phase and amplitude modulation, the chiral metasurfaces have broken through the weak chiroptical responses of natural media, giving birth to a number of unprecedented phenomena. However, the performance of passive metasurface is inadequate to realize dynamic manipulation to fit the diverse and changeable operation requirements, which would damage their engineering applications. Here, a circular dichroism meta-mirror consisting of Archimedean spiral-based meta-atoms is proposed to achieve dynamic scattering modulation. Combining the strategy of loading active element, the chiroptical responses of a metasurface is smoothly controlled. By controlling bias voltages, continuous scattered reflection amplitude steering can be achieved for the designated spin state while the orthogonal spin state can hardly be influenced. With the assistance of Pancharatnam-Berry phase principle, the metasurface possesses the capability of tailoring waves in coded manner. We experimentally verify the proposed strategy by a 1-bit checkerboard meta-mirror for four-beam scattering pattern. Importantly, the proposed paradigm may find applications in spin-sensitive systems and adaptive camouflage.
ABSTRACT
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.
