Recently, chalcogenide phase-change materials (PCMs) photonics have become an emerging research field because the optical properties of the PCMs undergo a dramatic change during the amorphous-crystalline phase transition. The chalcogenide PCMs can be efficiently switched by electrical or short optical pulses, offering versatility in photonic applications and extraordinary capability to engineer light. The authors introduce the fundamentals of chalcogenide PCM-tuned photonics. The progress in the field is reviewed. Particularly, recent developments of metal-chalcogenide-metal (MCM) trilayered plasmonic nanostructures are presented. The authors then discuss the methodology of designing reconfigurable MCM-based photonic devices, their advantages, and their existing challenges. Finally, requirements and prospects to successfully implement chalcogenide PCMs in growing areas of photonics are discussed. optical properties are required. As the PCM is heated by electrical or optical pulses, it can be crystallized (SET) and reamorphized (RESET), which not only significantly varies the electrical resistivity but also the optical properties of PCM. It is this photonic change that is applied to a variety of phase-change photonic systems. The chalcogenide PCM can be soundly switched >10 8 times before failure with a switching time < 500 ps, it is scalable, and many of its properties can be tailored through interface engineering. The purpose of this review is to introduce the concepts in chalcogenide PCM-engineered photonic devices and illustrate the role of the chalcogenide semiconductor in rapidly growing photonic applications ranging from optical data storage and display to their incorporation to reconfigurable or tunable metal-chalcogenide-metal (MCM) photonic devices. We believe this review will be of much interest to both photonics and PCM communities, resulting in new, improved PCMs specifically designed for integration with on-chip nanophotonic devices with functionalities on demand. MotivationThe traditional optical materials, for example, glasses lack tunability. Therefore, one has to precisely modulate the structural geometry of the device to change the functionality or operating frequency. This technique employed for the traditional optical materials, for example, glasses lack tunability. Therefore, one has to precisely modulate the structural geometry of the device to change the functionality or operating frequency. This technique employed for engineering the visible-infrared light relies on an accurate controlling of the geometry of the photonic nanostructure, which increases the complexity and cost of tunable optical systems. There are, however, lots of applications where dynamically reconfigurable photonic devices are highly desirable. In this regard, functional materials with either electrically or optically tunable parameters are technologically important and desirable. Over the past few years, more modern materials with tunable optical properties, such as liquid crystals, [7][8][9][10][11][12][13] graphene, [...

Metasurface-based structural coloration is a promising enabling technology for advanced optical encryption with a high-security level. Herein, we propose a paradigm of electrically switchable, polarization-sensitive optical encryption based on designed metasurfaces

Chiral metasurfaces can exhibit a strong circular dichroism, but it is limited by the complicated fabrication procedure and alignment errors. Here, a new type of self‐aligned suspended chiral bilayer metasurface with only one‐step electron beam lithography exposure is demonstrated. A significant optical chirality of 221° µm−1 can be realized using suspended metasurfaces with a thickness of 100 nm. Furthermore, this study experimentally demonstrates that such a structure is capable of label‐free discrimination of the chiral molecules at zeptomole level, exhibiting a much higher sensitivity (orders of magnitude) compared to the conventional circular dichroism spectroscopy. The fundamental principles for chiral sensing using molecules–metasurfaces interactions are explored. Benefiting from the giant chiroptical response, the proposed metadevice may offer promising applications for ultrathin circular polarizers, chiral molecular detectors, and asymmetry information processing.