Closing Editorial: Emerging Trends in Metamaterials and Metasurfaces Research

1. Introduction

Over the past two decades, metamaterials and metasurfaces [1,2,3] have profoundly transformed our understanding of how electromagnetic waves can be controlled, manipulated, or even engineered to obtain a desired electromagnetic response. By combining intrinsic material properties with carefully engineered subwavelength unit–cell architectures, these artificial media have enabled a myriad of responses that are inaccessible in naturally occurring materials. Over time, the field has evolved from early demonstrations of negative refractive index [4,5] and unusual dispersion properties into a mature research domain with broad impact across many areas ranging from photonics [6] to optoelectronics [7], communications [8], sensing [9], imaging [10], and energy-related applications [11,12,13]. As a result, metamaterials and metasurfaces are now positioned as key enabling platforms for next-generation photonic and electromagnetic systems [2,3,14,15].

This Special Issue, entitled Emerging Trends in Metamaterials and Metasurfaces Research, is intended to showcase these developments and provide a snapshot of the current research landscape. It aims to highlight recent advances that address both fundamental challenges and application-driven demands, while also pointing toward emerging directions that are likely to shape the future of this research field.

2. An Overview of the Articles in This Special Issue

The articles collected in this Special Issue exhibit a wide range of physical phenomena and application domains for metamaterials and metasurfaces research, highlighting the vast diversity of contemporary research in this field. Nevertheless, a prominent theme across the contributions is the emphasis on enhanced functionality through structural and material innovation, rather than relying on single-purpose or narrowband designs.

Several contributions explore advanced strategies for achieving broadband and ultra-broadband electromagnetic responses, particularly in absorptive and emissive metastructures operating from the ultraviolet and infrared regimes to terahertz frequencies. These works highlight how carefully engineered multilayer architectures, hybrid material platforms, and impedance-matching concepts can be combined to achieve high absorption efficiency, spectral selectivity, and energy-efficient operation—features that are increasingly important for sensing, thermal management, and infrared photonic technologies.

Another significant group of contributions focuses on active, reconfigurable, and programmable metasurfaces. By integrating phase-change materials, tunable conductive elements, or hybrid switching concepts, these studies demonstrate dynamic control over amplitude, phase, polarization, and transparency windows. Such approaches are particularly relevant for terahertz communications, adaptive beamforming, and electromagnetic modulation, where performance must be balanced against speed, power consumption, and material limitations.

This Special Issue also showcases advances in wavefront engineering and polarization control, including extreme birefringence, structured light manipulation, orbital angular momentum phenomena in engineered media, and even resonant electromagnetic deformation of nanostructures. These studies extend the capabilities of metasurfaces beyond conventional beam shaping, offering new degrees of freedom for information encoding, imaging, and optical signal processing, especially in anisotropic and isotropy-broken material platforms.

Complementing these physical and device-oriented contributions, several articles emphasize the growing role of advanced computational strategies. Numerical optimization and machine learning-assisted inverse designs are presented as powerful tools to overcome the complexity and computational burden traditionally associated with metasurface design, enabling faster development cycles and improved design accuracy for multifunctional and multichannel devices.

3. Conclusions and Future Perspectives

This Special Issue brings together a set of articles that illustrate the dynamic and rapidly evolving nature of metamaterials and metasurfaces research. Nevertheless, while remarkable progress has been made, the metamaterials field continues to face important challenges that will define its future trajectory. Issues such as broadband operation, low loss, fast tunability, and fabrication robustness are instrumental for moving the research from laboratory demonstrations toward integrated and scalable technologies.

In particular, the development of novel functional metasurfaces that are capable of real-time reconfiguration and autonomous response is expected to play a central role in future telecommunications, sensing, and imaging systems. Continued advances in active and phase-change materials, combined with innovative structural concepts, will be instrumental in overcoming the current limitations of these structures. At the same time, further investigation of the electromagnetic response in anisotropic, bianisotropic, and topological metadevices is more than likely to reveal new physical effects and functionalities, particularly in relation to structured light and angular momentum control.

An equally important and rapidly developing area in metamaterials and metasurfaces research is the integration of computational intelligence into the design process. Machine learning and hybrid analytical–numerical approaches are poised to become standard tools, enabling rapid exploration of large design spaces and facilitating the realization of highly complex, multifunctional devices.

In summary, this Special Issue offers the research community an opportunity to reflect on the trends shaping the present and future of metamaterials and metasurfaces research. We hope that this Special Issue will stimulate further research, foster new collaborations, and contribute to the continued advancement of metamaterials and metasurfaces as cornerstone technologies in modern photonics.