Design methodology for amplitude and phase low-coupling response in reconfigurable metasurfaces with enhanced energy focusing

Abstract This study introduces a reconfigurable metasurface composed of magnetorheological elastomers (MREs). The magnetically tunable properties of MREs enable continuous phase modulation of the metasurface units across the 0-2π range. The gradient phase distribution model is established in accordance with the Generalized Snell's Law, which enables the wavefield focusing and energy harvesting at different positions of the line source and the cylindrical wave source. Systematic simulations and experiments collectively demonstrate the effectiveness of this metasurface for flexural wave manipulation. This approach overcomes limitations of phononic crystals in energy harvesting, offering a novel magnetically controlled reconfigurable solution for flexural wave manipulation. It holds significant potential for engineering applications in structural health monitoring and vibration energy harvesting.

Reconfigurable metasurface holography in the visible region is hindered by the trade-off between optical loss and phase tunability. We report a reconfigurable visible metasurface hologram operated at a fixed wavelength, enabled by the reversible phase transition of an Sb2S3 phase-change metasurface. The device integrates nonvolatile switching with complementary polarization multiplexing and a computationally optimized phase framework to achieve on-demand control of multiple holographic channels without altering geometry. In the crystalline state, two distinct images are reconstructed under orthogonal linear polarizations (x and y), whereas in the amorphous state, two additional images are activated under left- and right-handed circular polarizations (LCP and RCP). An iterative Fourier-Adam optimization establishes a shared base phase that maintains interchannel orthogonality, suppressing crosstalk and enhancing reconstruction fidelity. The low-loss, nonvolatile Sb2S3 platform provides a scalable route toward compact optical encryption and programmable visible photonics.

Abstract Conventional electromagnetic cloaking paradigms predominantly necessitate the encasing of static objects within predefined topological enclosures, fundamentally restricting invisibility to fixed, closed geometries. Realizing dynamic, adaptive concealment for arbitrary moving targets within an open, boundary-free aperture remains a formidable challenge. Here, we report a meta-reinforcement-learning metasurface (Meta 2 Surface) that enables the first experimental demonstration of a "transparent cloaking tunnel" (TCT)—an open corridor permitting the undetected passage of diverse objects. Distinguished from traditional adaptive cloak, the Meta 2 Surface employs a sensor-in-the-loop meta-policy governed by a task-adaptive hypernetwork. This architecture fuses real-time sensing with historical interaction trajectories to instantly synthesize impedance strategies that actively nullify object-dependent scattering with millisecond-scale latency. Comprehensive full-wave simulations and microwave experiments confirm robust, high-fidelity cloaking of diverse dynamic targets—varying in shape, size, material, and trajectory—even under abrupt object substitution. By transitioning invisibility from static encapsulation to a dynamic, open architecture, this work establishes a new paradigm for fusing artificial intelligence with reconfigurable metasurfaces to achieve cognitive, large-scale electromagnetic wave control.

Abstract Continuously tunable phase-gradient metasurfaces offer powerful capabilities for dynamic and adaptive optics, but their practical realization remains challenging due to the complexity of device control architectures, especially when compared to binary or discretely tunable systems. In this perspective, we outline a unifying framework that leverages inverse design principles to enable scalable implementation of reconfigurable metasurfaces. We begin by reviewing three core innovations from our earlier work on phase change material (PCM) based varifocal metalenses: thermal profile shaping via patterned doping, phase-gradient tuning through direct search optical inverse design, and pixel-level wavefront control using phase-change metasurface arrays. We then highlight recent advances that build upon these foundations: an analytical, geometry-independent thermal inverse design method for microheater profile customization; the generalization of phase-gradient tuning to alternative actuation mechanisms including coherent optical control; and the experimental realization of a mid-infrared (mid-IR) two-dimensional spatial light modulator (2D SLM) based on diode-integrated PCM metasurfaces. Together, these developments demonstrate a path from architectural insight to scalable implementation, opening new opportunities for high-performance, programmable optical systems in imaging, beam shaping, and beyond.

Dual-Polarized Reconfigurable Metasurface for Wideband RCS Reduction At Extremely Oblique Incidence

Abstract In this paper, we propose a switchable high-Q light absorber based on a reconfigurable metasurface enabled by a lowloss phase-change material (PCM). By leveraging the coupling between guided-mode resonance and Fabry–Perot modes, mediated by the phase-transition dynamics of the embedded PCM, the resonance Q factor can be actively tuned. This allows the system to switch from a perfect dark state, governed by the physics of bound states in the continuum, to a critically coupled resonance with a finite Q factor. Consequently, the metasurface exhibits perfect absorption in the amorphous state and a reflection-dominated response in the crystalline state. The proposed metasurface holds significant potential for diverse nanophotonic applications, including photodetection and thermal emission control.

Previous studies on reconfigurable intelligent metasurface (RIS) design have primarily relied on full-wave electromagnetic simulation software, which often incurs high computational costs and lacks clear design direction. The design of multi-bit RIS remains challenging and there is currently no suitable systematic method for selecting the corresponding tuning devices. To overcome these limitations, this article proposes a novel equivalent circuit-based approach to RIS design. In contrast to the conventional approach, where the equivalent circuit model is derived from post-design evaluation of the scattering properties of RIS, our work is entirely driven by the equivalent circuit model from the outset to accomplish the unit cell design. A complete workflow as well as details of each constituent step are presented for the topology design of RIS based on equivalent circuit topology. Building on this circuit topology, a 3-bit reflective phase reconfigurable unit cell is developed based on a tunable band-stop filter circuit. We conducted adjustable phase verification experiments and beam deflection experiments. The consistency between the experimental results and circuit theory demonstrates the feasibility and practicality of the equivalent circuit method of RIS design. This circuit-to-structure methodology provides a physically interpretable and systematic framework for designing RIS with arbitrary electromagnetic responses, offering new insights into RIS design.

The emergence of tunable metasurfaces has paved the way for dynamic infrared manipulation and played a crucial role in advancing applications such as biochemical sensing and infrared imaging. In this paper, we present a micromachined tunable narrowband thermal emitter with a wide tuning range and a high quality factor by integrating microelectromechanical system (MEMS) reconfigurable metasurfaces with on-chip micro-heaters. Due to the resonance mode coupling of the metasurface and Fabry–Perot cavity, the emission peak can be modulated from 2–14 μm by continuously altering the thickness of the air gap. A versatile scheme for constructing a MEMS reconfigurable metasurface is proposed by combining free-standing all-metallic metasurfaces and silicon-based MEMS actuators, which can eliminate the intrinsic losses and multiple resonances in substrates, substantially increasing the spectral resolutions. A wafer-scaled MEMS microfabrication process is developed and implemented for the devices, indicating a potential for mass production. We further fabricate miniaturized tunable metasurface thermal emitters, realizing a tuning range covering the long wavelength infrared range and experimentally demonstrating the thermal emission capability as well. Our design provides a practical and effective solution for realizing a real-time thermal emission control with high performance and has a promising prospect in achieving highly integrated, low-cost dynamic infrared meta-devices.

Abstract Increasingly complex electromagnetic environments and congested spectral resources demand the crucial frequency-selective filtering to suppress out-of-band interference during wave manipulation. Here, we present a stacked reconfigurable metasurface that achieves sharp frequency filtering together with multidimensional tunability across polarization and spectral domains. This stacking strategy decouples polarization channels and tailors near-field coupling to realize controllable frequency shifts. A transmission-line theory is analytically established to characterize and control the scattering poles and zeros under varying polarizations and bias voltages, thereby enabling the prediction of the metasurface’s tunable filtering behavior. Experiments validate dynamic polarization selection and continuous shifting of the filtering band. The measured bandpass response exhibits steep transition edges and strong out-of-band rejection, effectively isolating adjacent spectral channels. This design demonstrates the integration of tunability and selectivity across multiple wave dimensions, addressing critical demands for reconfigurability, multiplexing, and interference immunity in modern electromagnetic systems, with broad potential for smart sensing, secure communications, and radar technologies.

Reconfigurable metasurfaces seamlessly integrate physical and digital spaces and hold significant application prospects in 5G networks and the upcoming 6G technology. Despite rapid technological advancements, integrating full-space beam control and stealth capabilities within a single metasurface operating in the terahertz (THz) band, while achieving software-customizable electromagnetic regulation capabilities, remains a major challenge. In this paper, an omnidirectional optically controlled terahertz reconfigurable metasurface (OOCTRM) is proposed, which integrates three modes: reflective regulation, transmissive regulation, and electromagnetic stealth. This metasurface exhibits a series of dynamic functions, including full-space multi-beam regulation and dynamic modulation of multi-mode orbital angular momentum (OAM). Additionally, a multifunctional beam control system featuring the collaborative design of a physical sensing layer, an algorithm optimization layer, and a real-time interaction layer is proposed herein. The system we proposed can dynamically and independently regulate full-space THz beams in a software-defined manner. At the real-time interaction layer, we designed a visual interface that enables real-time monitoring of coding states, beam regulation, and other related conditions. This study is expected to offer a promising approach for manipulating transmitted terahertz beams via light-controlled reconfigurable metasurfaces and holds great potential for integrated stealth communication systems, intelligent sensing, and terahertz wireless communications.

The advancement of terahertz (THz) integrated photonic circuits is critically dependent on the development of compact, dynamically reconfigurable components for signal routing and manipulation. In this work, we propose and systematically analyze a novel, to our knowledge, graphene-on-insulator plasmonic power divider designed for high-efficiency operation in the THz regime. The device’s performance is investigated through rigorous finite-difference time-domain (FDTD) simulations, exploring the impact of key parameters including the graphene chemical potential (from 0 to 0.5 eV), the number of graphene layers (1–3), and the geometric dimensions of the waveguide structure. Our analysis reveals that a strategic reduction of the central coupling waveguide’s length, combined with the implementation of a three-layer graphene structure, dramatically enhances plasmon confinement and minimizes propagation and reflection losses. The optimized configuration demonstrates a peak power transmission efficiency of 93.46% at 12.36 THz. Furthermore, the device maintains an exceptionally wide and stable operational bandwidth, with transmission exceeding 90% across an extensive frequency range from 5.1 to 25.1 THz. These results establish a clear design pathway for realizing highly efficient and actively tunable plasmonic components, paving the way for next-generation reconfigurable THz metasurfaces, switches, and complex integrated photonic systems.

Light beams carrying spin angular momentum (SAM) and orbital angular momentum (OAM) have garnered significant interest owing to their potential in optical communications, imaging, and micromanipulation. Although simultaneous detection of multiple SAM and OAM modes through demultiplexing is highly necessary, it remains challenging due to the static optical responses of conventional metasurfaces after device fabrication. Here, we propose a multifunctional metasurface demultiplexer utilizing the phase-change material Ge2Sb2Se4Te1 (GSST) for reconfigurable, simultaneous detection of multiple SAM and OAM modes. When GSST is amorphous, the coaxial beams carrying SAM and OAM modes are spatially demultiplexed into distinct vortex beams with defined topological charges, and each propagates to a predetermined position. The information of SAM and OAM of the incident beam can be determined by observing the position of the solid spot. Upon transition of GSST into the crystalline state, demultiplexing ceases due to the loss of phase modulation capability, thereby preventing mode retrieval. This reconfigurable detection strategy offers a promising platform for dynamically switchable devices in applications such as encrypted optical communications and dynamic holography.

We develop an autonomous experimentation platform to accelerate interpretable scientific discovery in ultrafast nanophotonics, targeting a novel method to steer spontaneous emission from reconfigurable semiconductor metasurfaces. Despite the potential of reconfigurable semiconductor metasurfaces with embedded sources for spatiotemporal control, achieving arbitrary far-field control remains challenging. Here, we present a self-driving lab (SDL) platform that addresses this challenge by discovering the governing equations for predicting the far-field emission profile from light-emitting metasurfaces. We discover that both the spatial gradient (grating-like) and the curvature (lens-like) of the local refractive index are key factors in steering spontaneous emission. The SDL employs a machine-learning framework comprising: (1) a variational autoencoder for generating complex spatial refractive index profiles, (2) an active learning agent for guiding experiments with real-time closed-loop feedback, and (3) a neural network-based equation learner to uncover structure-property relationships. The SDL demonstrates up to a four-fold enhancement in peak emission directivity (up to 77%) over a 74° field of view within ~300 experiments. Our findings reveal that combinations of positive gratings and lenses are as effective as negative lenses and gratings for all emission angles, offering a novel strategy for controlling spontaneous emission beyond conventional Fourier optics.

Abstract Reconfigurable metasurfaces exhibit remarkable capabilities in suppressing radar scattering signatures, but their effectiveness is often constrained by a single modulation mechanism. This work proposes an ultra‐wideband radar cross section (RCS) reduction metasurface based on height‐tunable absorbing unit cells actuated by shape memory alloy (SMA) springs. This design integrates a three‐layer lossy absorber for broadband low‐frequency absorption with dynamic phase modulation of sub‐blocks, achieving frequency‐controllable scattering manipulation through phase cancellation. By electrically tuning the bias voltages applied to the SMA springs, the metasurface can switch among strong absorption, frequency‐tunable scattering, and ultra‐wideband RCS reduction states. Experimental results show a broadband high absorption in the range of 4–12 GHz, while height tuning of the SMA‐actuated elements enables frequency‐controllable RCS reduction from 16.1 to 36.3 GHz. In the integrated state, a superior 20 dB RCS reduction is achieved across 4.2–40 GHz. Moreover, the metasurface maintains robust performance under wide‐angle incidence and different polarizations, demonstrating great potential for adaptive scattering control and dynamic camouflage applications.

A reconfigurable metasurface with independent dynamic modulation of transmission and absorption

The multi-dimensional dynamic manipulation and integration of topological optical fields are crucial for advancing the application of terahertz (THz) metasurfaces in high-dimensional information processing and on-chip photonics. However, current THz metasurfaces face challenges such as insufficient reconfigurability and limited mode manipulation freedom. These hinder the dynamic generation and switching of complex topological modes. In this paper, we present a dynamically reconfigurable THz metasurface device based on vanadium dioxide (VO2) phase-change material, achieving the integration and switching of multiple topological optical field states within the same structure for the first time. In the VO2 insulating state (T < 68°C), we use symmetry-protected bound states in the continuum (BIC) to excite spatial vortex light and second-order Meron spin textures in transmission. This establishes a topological mapping between real space and momentum space. The reflection channel exhibits a spin-Hall shift with adjustable incident chirality. Upon the phase transition of VO2 to the high-temperature metallic state, the BIC evolves into a quasi-BIC state, leading to the realization of radiation output of spatiotemporal vortex light. Simulations show the device maintains stable singular optical fields over a broad frequency band. This enables all-optical dynamic switching via thermal control and incident polarization. This research offers novel insights into topological multiplexing in the THz band, spatiotemporal dimension information coding, and the design of high-dimensional quantum optical devices.

Dynamically tunable metasurfaces based on phase-change materials (PCMs) have become important platforms for realizing reconfigurable optical systems. Nevertheless, achieving multiple independent functionalities within a single device, particularly under polarization multiplexing, remains difficult due to limited design flexibility. In this study, we present a metasurface design framework that reaches the theoretical maximum of six independent phase modulation functions by simultaneously controlling the polarization states and the crystallinity of the PCM. This is implemented through a pixel-extension strategy, where each nanofin functions independently in amorphous state and is reorganized into superpixels with distinct optical responses in crystalline state. To support this, a forward filtering algorithm is developed to efficiently determine structural configurations under dual-state constraints. The effectiveness of the proposed approach is confirmed through two representative implementations, including dynamically switchable multifocal metalenses and multichannel holography. In addition, a progressive encoding strategy is introduced, which deliberately utilizes inter-state crosstalk to hierarchically embed optical information across material states. This compact and reconfigurable metasurface platform offers high functional density and flexible control, holding strong potential for applications in optical communication, information encryption, and adaptive display technologies.

Wireless cellular stimulation has been widely applied for bioengineering and bidirectional communication with the brain. Different technologies, such as photoelectrical stimulation as an alternative to optogenetics, have emerged for a wide range of remote therapeutic applications using light. Metasurfaces enable pixel-wise control of electric field distribution by engineering absorption and wavefront shaping, with responses tuned to incident light polarization, frequency, and phase, offering precise stimulation and wireless control in retinal, cochlear, and cardiac implants. Moreover, by leveraging terahertz (THz) band patches, reconfigurable metasurfaces controlled via FPGA and holography, and virtual reality-assisted designs, these interfaces can revolutionize bioelectronic medicine.

Abstract Terahertz communication promises Tbit/s-level connectivity for 6G but is hindered by severe path loss and atmospheric absorption. While reconfigurable metasurfaces offer a promising solution via dynamic wavefront control, conventional design relying on empirical optimization and constrained geometric templates inherently restricts phase tuning ranges. To address on these limitations, we propose an intelligent inverse design framework for liquid crystal metasurface with three synergistic innovations: (1) A non-uniform rational B-splines method is introduced to explore smooth topological geometries of metallic patterns, reducing the solution space from 100 to 8 degrees of freedom and simplifying subsequent optimization; (2) A hybrid convolutional neural network−Transformer model is developed to jointly learn local and global electromagnetic features, achieving high prediction accuracy (phase error: 1.03°, amplitude error: 2.8×10-3); (3) The proposed network is integrated with a particle swarm optimization algorithm for inverse design, rapidly identifying the globally optimal design within high-dimensional parameter spaces across 0.25−0.55 THz. Finally, the optimized metasurface achieves 310° phase tuning and &gt;0.9 reflectance, with the LC thickness being only 1.4% of the working wavelength, surpassing the performance in prior literature. Based on array-level optimization algorithms, we further demonstrate highly directional beam steering with flexible control over beam quantity, power ratio, and beamwidth. This work presents an innovative design approach for reconfigurable terahertz metasurfaces, paving the way for their practical implementation in next-generation communication systems.