The inevitable feedback between the environmental and energy crisis within the next decades can probably trigger and/or promote a global imbalance in both financial and public health terms. To handle this difficult situation, in the last decades, many different classes of materials have been recruited to assist in the management, production, and storage of so-called clean energy. Probably, ferromagnets, superconductors and ferroelectric/piezoelectric materials stand at the frontline of applications that relate to clean energy. For instance, ferromagnets are usually employed in wind turbines, superconductors are commonly used in storage facilities and ferroelectric/piezoelectric materials are employed for the harvesting of stray energy from the ambient environment. In this work, we focus on the wide family of ferroelectric/piezoelectric materials, reviewing their physical properties in close connection to their application in the field of clean energy. Among other compounds, we focus on the archetypal compound Pb(Zr,Ti)O3 (or PZT), which is well studied and thus preferred for its reliable performance in applications. Also, we pay special attention to the advanced ferroelectric relaxor compound (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (or PMN-xPT) due to its superior performance. The inhomogeneous composition that many kinds of such materials exhibit at the so-called morphotropic phase boundary is reviewed in connection to possible advantages that it may bring when applications are considered.

Active tuning of the scattering of particles and metasurfaces is a highly sought-after property for a host of electromagnetic and photonic applications, but it normally requires challenging-to-control tunable (reconfigurable) or active (gain) media. Here, we introduce the concepts of anisotropic virtual gain and oblique Kerker effect, where a completely lossy anisotropic medium behaves exactly as its anisotropic gain counterpart upon excitation by a synthetic complex-frequency wave. The strategy allows one to largely tune the magnitude and angle of a particle’s scattering simply by changing the shape (envelope) of the incoming radiation, rather than by an involved medium-tuning mechanism. The so-attained anisotropic virtual gain enables directional super-scattering at an oblique direction with fine-management of the scattering angle. Our study is based on analytical techniques that allow multipolar decomposition of the scattered field in agreement with full-wave simulations, and lays the foundations for a light management method.

Metasurfaces are capable of fully reshaping the wavefronts of incident beams in desiredmanners.However,therequirementforexternallightexcitationand the resonant nature of their meta-atoms, make challenging their on-chip integration. Here, we introduce the conceptanddesignofafreshclassof metasurfaces, driven by unidirectional guided waves, capable of arbitrary wavefront control based on the uniquedispersion properties of unidirectional guided waves rather than resonant meta-atoms. Upon experimentally demonstrating the feasibility of our designs in the microwave regime, we numerically validate the introduced principle through the design of several microwave meta-devices using metal-air-gyromagnetic unidirectional surface magneto-plasmons, agilely converting unidirectional guided modes into the wavefrontsof3DBesselbeams,focusedwaves,andcontrollablevortexbeams. We, further, numerically demonstrate sub-diffraction focusing, which is beyond the capability of conventional metasurfaces. Our unfamiliar yet prac tical designs may enable full, broadband manipulation of electromagnetic waves on deep subwavelength scales.

In this letter, we demonstrate that a set of absorbing boundary conditions (ABCs) for numerical simulations of waves, proposed originally by Engquist and Majda and later generalized by Trefethen and Halpern, can alternatively be derived with the use of Pauli matrices algebra. Hence a novel approach to the derivation of one-way wave equations in electromagnetics is proposed. That is, the classical wave equation can be factorized into two two-dimensional wave equations with first-order time derivatives. Then, using suitable approximations, not only Engquist and Majda ABCs can be obtained, but also generalized ABCs proposed by Trefethen and Halpern, which are applicable to simulations of radiation problems.

In the past two decades, index-near-zero (INZ) modes and materials, with their spatial phase invariance and super coupling, gained increasing attention for applications in all-optical/quantum computing and communication. However, the modulation of INZ modes is typically complex and discontinuous, often achieved through intricate experimental methods, thereby hindering their widespread application. Here, we propose two deep-subwavelength magneto-optical one-way waveguides and discover three broadband tunable INZ modes, exhibiting predict able behavior dependent on the external magnetic field (EMF). By utilizing these INZ modes, we design broadband tunable all-optical phase modulators through straightforward EMF control. The tunable and predictable nature of INZ modes, combined with deep-subwavelength phase modulators, may advance miniaturized all-optical communication and computation.