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Extreme light confinement observed in periodic photonic structures, such as the vortex singularities in momentum (k) space, has been associated with their topological nature. Consequently, by exploiting and tuning their topological properties, optical metasurfaces have been demonstrated as an attractive platform for active photonics. However, given the fact that most active media under external excitations can only provide limited refractive index change, the potential advancements offered by the topological character of active metasurfaces have remained mostly unexplored. Zinc oxide (ZnO), which has recently exhibited optically-induced extraordinarily large permittivity modulations at visible and near-infrared frequencies, is an excellent active material for dynamic metasurfaces exhibiting strong tuning. This work demonstrates that a hybrid metasurface consisting of an array of ZnO nanodisks on a silver backplane displays broadly tunable topological properties. In particular, by performing k-space scattering simulations using measured pump-fluence-dependent material properties of ZnO, we study in detail the light reflection from the hybrid metasurface. Our results validate that the large k-space topology tuning of the metasurface can result in enormously strong polarization manipulation of near-infrared light in the vicinity of the topological features. The observed polarization switching effect is highly sensitive to the polarization and wavelength of an incident wave, owing to the symmetry and dispersion characteristics of the proposed system. Our study indicates that leveraging a combination of the extraordinary material properties and the k-space topology, hybrid metasurfaces based on ZnO may open new avenues for creating all-optical switchable metadevices.

Opening a new door to tailoring electromagnetic (EM) waves, temporal boundaries have attracted the attention of researchers in recent years, which have led to many intriguing applications. However, the current theoretical approaches are far from enough to handle the complicated temporal systems. In this paper, we develop universal matrix formalism, paired with a unique coordinate transformation technique. The approach can effectively deal with temporally stratified structures with complicated material anisotropy and arbitrary incidence angles. This formulation is applied to various practical systems, enabling the solution of these temporal boundary related problems in a simple and elegant fashion, and also facilitating a deep insight into the fundamental physics.

In this paper, an efficient transient analysis method with arbitrary high-order accuracy for nonlinear field-circuit co-simulation problems is proposed. The proposed method combines a local time-stepping (LTS) technique with the discontinuous Galerkin time-domain (DGTD) method based on an arbitrary high-order derivatives (ADER) time integration scheme. The stability of the proposed method is not limited by the global time step size, allowing nonlinear and linear elements to update themselves with individual and optimal time intervals in accordance with the local stability condition. It is shown that the efficiency of the proposed method can be significantly improved when the nonlinear effects increase, which requires a smaller time interval to ensure system convergence. Several field-circuit coupling structures are simulated to demonstrate the accuracy and efficiency of the proposed method, confirming that it represents an effective tool for transient analysis of nonlinear field-circuit structures.

Reconfigurable electromagnetic devices, specifically reconfigurable antennas, have shown to be integral to the future of communication systems. However, mechanically robust designs that can survive real-world, harsh environment applications and high-power conditions remain rare to this day. In this paper, the general framework for a field of both discrete and continuously mechanically reconfigurable devices is established by combining compliant mechanisms with electromagnetics. To exemplify this new concept, a reconfigurable compliant mechanism antenna is demonstrated which exhibits continuously tunable performance across a broad band of frequencies. Moreover, three additional examples are also introduced that further showcase the versatility and advanced capabilities of compliant mechanism enabled electromagnetic devices. Unlike previous approaches, this is achieved with minimal part counts, additive manufacturing techniques, and high reliability, which mechanical compliant mechanism devices are known for. The results presented exemplify how compliant mechanisms have the capacity to transform the broader field of reconfigurable electromagnetic devices.

In this article, a compact triple-port dual-band triple-mode antenna enabled by a shielded mushroom structure with operational bands centered at 2.4 and 5.8 GHz is proposed possessing both pattern and polarization diversities. By tailoring the dispersive properties of the artificial transmission line (ATL) cells and structuring them into a multilayer architecture, the integrated antenna is capable of generating vertically polarized, $y$ -horizontally polarized, and $x$ -horizontally polarized radiation patterns simultaneously at two predefined bands with good port isolations and field orthogonality. The design concept and the analysis of the ATL cells in the form of shielded mushrooms are described, illustrating the dual-band operating principle of the antenna. A proof-of-concept antenna is designed with a footprint of $0.48\lambda _{0}^{2}$ and a profile of $0.07\lambda _{0}$ , where $\lambda _{0}$ is the free space wavelength at 2.4 GHz. The proposed antenna was fabricated and characterized, achieving measured $S_{11} dB bandwidths of 35 and 85 MHz in the two targeted bands, respectively, with mutual coupling smaller than −15 dB and envelope correlation coefficients below 0.01 for all three ports. Moreover, it is shown that the two operational bands of the antenna can be independently controlled, which reveals the unprecedented degrees-of-freedom in its design. The demonstrated dual-band triple-mode antenna is highly useful for dual-band multimode wireless devices and dual-band multiple-input multiple-out communication systems.

Throughout nature, simple rules explain complex phenomena, such as the selective interaction of chiral objects with circularly polarized light. Here, we demonstrate chiroptical signals from gold na...

The previously developed heuristic uniform theory of diffraction corner and wedge diffraction coefficients for a thin lossless anisotropic slab are generalized and applied for predicting electromagnetic scattering by a lossy/lossless multilayer anisotropic slab. The effective reflection and transmission coefficients of a multilayer slab are used in the heuristic formulation to determine the scattered fields. The heuristic coefficients derived for a thin slab are applied to a multilayer slab with a finite thickness. Numerical results are provided for various scattering problems that demonstrate the validity of the heuristic formulations for a multilayer structure.

The rise and proliferation of artificial intelligence (AI) has the potential to influence and disrupt many aspects of society as we currently know it. While it has been a long-held belief that robots are limited to physical tasks and therefore only capable of replacing blue collar workers, many concerns exist that continued developments will yield artificial minds capable of replacing knowledge workers. These advancements have led people to ask the question, "What will our society look like when AI is everywhere?" [1].

In this article, the theory, design, and validation of planar array antennas capable of producing dual-circularly-polarized (dual-CP) dual-beam radiation with a single feeding network are reported. Importantly, the properties of the formed CP beams with different handedness can be independently controlled. Such a capability is achieved by exploiting both the in-plane rotation-induced Berry phase and excitation phase for all the linearly polarized array elements, which can be regarded as a generalization of the well-known sequential rotation arrays. Microstrip patch arrays with such single-feed dual-CP dual-beam functionalities can be synthesized through a straightforward analytical approach that accurately predicts the radiation patterns for both right- and left-handed CP beams. The proposed technique and design methodology were verified by two proof-of-concept microstrip arrays consisting of $8 \times 8$ linearly polarized circular patch elements operating in the $K$ -band, one with uniform excitation amplitudes and the other with tapered excitations for sidelobe suppression. Both arrays were fabricated and measured, experimentally achieving a joint $S_{11} dB, axial ratio < 3 dB, and 3 dB gain bandwidth of more than 22.5%/20.0% and 16.7%/15.8%, respectively, for the right- and left-handed CP beams. Within this broad operational band, the beam squinting is on average within ±3°. The proposed dual-CP dual-beam arrays have fully planarized structures, low profiles, wide operational bandwidths, and high polarization purity, making them useful candidates for applications including satellite communications, point-to-multipoint communications, and so on.