No abstract

Since the advent of digital coding metamaterials, a new paradigm is unfolded to sample, compute and program electromagnetic waves in real time with one physical configuration. However, one inconvenient truth is that actively tunable building blocks such as diodes, varactors, and biased lines must be individually controlled by a computer‐assisted field programmable gate array and physically connected by electrical wires to the power suppliers. This issue becomes more formidable when more elements are needed for more advanced and multitasked metadevices and metasystems. Here, a remote‐mode metasurface is proposed and realized that is addressed and tuned by illuminating light. By tuning the intensity of light‐emitting diode light, a digital coding metasurface composed of such light‐addressable elements enables dynamically reconfigurable radiation beams in a control‐circuitry‐free way. Experimental demonstration is validated at microwave frequencies. The proposed dynamical remote‐tuning metasurface paves a way for constructing unprecedented digital metasurfaces in a noncontact remote fashion.

Programmable metasurfaces allow dynamic and real‐time control of electromagnetic (EM) waves in subwavelength resolution, holding extraordinary potentials to establish meta‐systems. Achieving independent and real‐time controls of orthogonally‐polarized EM waves via the programmable metasurface is attractive for many applications, but remains considerably challenging. Here, a polarization‐controlled dual‐programmable metasurface (PDPM) with modular control circuits is proposed, which enables a dibit encoding capability in modifying the phase profiles of x‐ and y‐polarized waves individually. The constructed extended interface circuit is able to extend the number of control interfaces from a field programmable gate array by orders of magnitude and also possesses memory function, which enhance hugely the rewritability, scalability, reliability, and stability of PDPM. As a proof‐of‐concept, a wave‐based exclusive‐OR logic gate platform for spin control of circularly‐polarized waves, a fixed‐frequency wide‐angle dual‐beam scanning system, and a dual‐polarized shared‐aperture antenna are demonstrated using a single PDPM. The proposed PDPM opens up avenues for realizing more advanced and integrated multifunctional devices and systems that have two independent polarization‐controlled signal channels, which may find many applications in future‐oriented intelligent communication, imaging, and computing technologies.

Signal conversion plays an important role in many applications such as communication, sensing, and imaging. Realizing signal conversion between optical and microwave frequencies is a crucial step to construct hybrid communication systems that combine both optical and microwave wireless technologies to achieve better features, which are highly desirable in the future wireless communications. However, such a signal conversion process typically requires a complicated relay to perform multiple operations, which will consume additional hardware/time/energy resources. Here, we report a light-to-microwave transmitter based on the time-varying and programmable metasurface integrated with a high-speed photoelectric detection circuit into a hybrid. Such a transmitter can convert a light intensity signal to two microwave binary frequency shift keying signals by using the dispersion characteristics of the metasurface to implement the frequency division multiplexing. To illustrate the metasurface-based transmitter, a hybrid wireless communication system that allows dual-channel data transmissions in a light-to-microwave link is demonstrated, and the experimental results show that two different videos can be transmitted and received simultaneously and independently. Our metasurface-enabled signal conversion solution may enrich the functionalities of metasurfaces, and could also stimulate new information-oriented applications.

A great challenge with metasurfaces is tunability for tailoring electromagnetic waves dynamically. Metasurfaces designed digitally, also known as digital coding metasurfaces, provide a low-overhead strategy for constructing controllable or even programmable metasurfaces. However, most reported digital metasurfaces have been single-band ones of the reflection type that have been realized by controlling the phase response of the digital elements. This study reports on a light-controllable and frequency-dependent digital coding metasurface that allows wave transmission to be manipulated more freely and flexibly. By remotely tuning the illumination intensity or shifting the frequency of the incident waves, the transmission response of the designed digital elements can be tuned dynamically. The proposed device is assessed experimentally at microwave frequencies. The presented transmissive digital metasurface offers unprecedented opportunities to produce reconfigurable devices that are controlled in multiple ways with a single design.

Invisibility cloaks, a class of attractive devices that can hide objects from external observers, have become practical reality owing to the advent of metamaterials. In previous cloaking schemes, almost all demonstrated cloaks are time‐invariant and are investigated in the system that is motionless, and hence they are limited to hide stationary objects. In addition, the current cloaks are typically static or require manual operation to achieve dynamic cloaking. Here, a smart Doppler cloak operating in broadband and full polarizations is reported, which consists of a time‐modulated reflective metasurface and a sensing‐feedback time‐varying electronic control system. Experimental results show that the smart Doppler cloak is able to respond self‐adaptively and rapidly to the ever‐changing velocity of moving objects and then cancel different Doppler shifts in real time, without any human intervention. Moreover, the wideband and polarization‐insensitive features enable the cloak to be more robust and practical. To illustrate the capabilities of the proposed approach, the smart Doppler cloak is measured in three scenarios with two different groups of linearly‐polarized incidences at 3.3 and 4.9 GHz, and one group circularly‐polarized incidences at 6.0 GHz, respectively.

No abstract

Nonlinear metamaterials are of continuing interest by manipulating electromagnetic (EM) waves depending on incident intensity. Most of the existing nonlinear metamaterials rely on the interactions between superconcentrated EM fields and nonlinear substances within the resonant composites, which cannot be easily adjusted dynamically. Here, an intensity‐dependent metasurface is proposed, whose nonlinearity distribution is digitally reconfigurable. Different from previous works, an active microwave detecting circuit is integrated into each particle of the metasurface as the nonlinear module, endowing reflection phase of the particle with strong dependence on microwave intensities. By controlling the circuit using a digital bit, the particle can be switched to be linear with a fixed phase, which provides a digital way to reconfigure the arrangement of nonlinear and linear particles on the metasurface. Therefore, the phase profile on the surface is determined by the incoming intensity and digital controlling signals, opening up new possibilities in nonlinear EM wave manipulations. The concept is demonstrated by the digitally defined nonlinear scattering measurements at microwave frequencies. As a new metamaterial with the digitally reconfigurable nonlinearity and negligible thickness, this proposal may find potential applications including power protection, EM compatibility, nonlinear beam scanning, and so on.