RESUMEN
Photon-electron interactions are essential for many areas such as energy conversion, signal processing, and emerging quantum science. However, the current demonstrations are typically targeted to fiber and on-chip applications and lack of study in wave space. Here, we introduce a concept of optoelectronic metasurface that is capable of realizing direct and efficient optical-microwave interactions in free space. The optoelectronic metasurface is realized via a hybrid integration of microwave resonant meta-structures with a photoresponsive material. As a proof of concept, we construct an ultrathin optoelectronic metasurface using photodiodes that is bias free, which is modeled and analyzed theoretically by using the light-driven electronic excitation principle and microwave network theory. The incident laser and microwave from the free space will interact with the photodiode-based metasurface simultaneously and generate strong laser-microwave coupling, where the phase of output microwave depends on the input laser intensity. We experimentally verify that the reflected microwave phase of the optoelectronic metasurface decreases as the incident laser power becomes large, providing a distinct strategy to control the vector fields by the power intensity. Our results offer fundamentally new understanding of the metasurface capabilities and the wave-matter interactions in hybrid materials.
RESUMEN
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.
RESUMEN
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.
RESUMEN
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.
RESUMEN
Programmable metasurface enables controlling electromagnetic (EM) waves in real time. By programming the states of active device embedded in metasurface element, the EM properties of the digital metasurface can be changed quickly without redesigning their structures. However, large numbers of long-distance wires are required to connect the programmable metasurface to provide the coded signals from field programmable gate array (FPGA) when controlling the metasurface at a long distance, which is complicated and inconvenient. Here, we propose an infrared-controlled programmable metasurface that can be programmed remotely. The infrared transceiver is able to switch the coding sequences stored in the FPGA controller, thus controlling the voltage on the varactors integrated in the metasurface. Experiment is performed at microwave frequencies, and the measured results verify that the scattering beams of the metasurface sample can be changed remotely by using infrared ray. The proposed infrared-controlled programmable metasurface opens up avenues for constructing a new class of remotely-tuning dynamic metasurfaces.
