Abstract
Abstract With their ultrathin characteristics as well as the powerful and flexible capabilities of wavefront modulation, optical metasurfaces have brought a new understanding of the interaction between light and matter and provided a powerful way to constrain and manage light. However, the unmodifiable structures and the immutable materials used in the construction lead to the unsatisfactory applications in most functional devices. The emergence of tunable optical metasurfaces breaks the aforementioned limitations and enables us to achieve dynamic control of the optical response. The work in recent years has focused on achieving tunability of optical metasurfaces through material property transition and structural reconfiguration. In this review, some tunable optical metasurfaces in recent years are introduced and summarized, as well as the advantages and limitations of various materials and mechanisms used for this purpose. The corresponding applications in functional devices based on tunability are also discussed. The review is terminated with a short section on the possible future developments and perspectives for future applications.
Highlights
Optical metasurfaces are subwavelength layers with patterns that interact strongly with light, dramatically altering the light properties over subwavelength thickness [1]
Existing research has promoted the development of functional optical and electromagnetic devices, such as data storage and encryption [5, 6], polarization conversion [7], holographic imaging [8, 9], metalenses [10, 11], nonlinear photonic elements [12, 13]. They have revolutionized our methods of management and restraint of light, most of the metasurfaces are static and focus on the specific optical response produced by the fixed structures and the immutability of the materials used in their construction
It is well known that phasechange materials (PCMs) can be applied in constructing tunable metasurfaces because these active materials will change among different states with various optical properties under proper external stimuli
Summary
Optical metasurfaces are subwavelength layers with patterns that interact strongly with light, dramatically altering the light properties over subwavelength thickness [1]. Existing research has promoted the development of functional optical and electromagnetic devices, such as data storage and encryption [5, 6], polarization conversion [7], holographic imaging [8, 9], metalenses [10, 11], nonlinear photonic elements [12, 13] They have revolutionized our methods of management and restraint of light, most of the metasurfaces are static and focus on the specific optical response produced by the fixed structures and the immutability of the materials used in their construction. One way is to switch the active materials into different states through various modulation mechanisms, which often means a changeable refractive index (dielectric constant) In this way, metasurfaces with active material can be modulated under external stimuli including thermal, electrical, magnetic, optical, chemical, or electrochemical methods [15]. We envision the future development of the tunable optical metasurface technology and applications
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