Tunable Metasurfaces: The Path to Fully Active Nanophotonics

Abstract

In the field of nanophotonics, metasurfaces have come to the forefront in real‐world applications, owing to their accessible exotic optical properties that can be readily designed and fabricated using currently available techniques. The subwavelength dimensions and lightweight characteristics of metasurfaces are attractive qualities for the miniaturization of optical devices and are already exploited in devices that can rival, and sometimes even outperform, conventional bulky optics. Over the past decade, ample research has been undertaken to produce high‐performance metasurfaces with exciting optical properties that cannot be found in nature or achieved with conventional optics. To open the path to widely used devices in our everyday lives, the next obvious step for metasurfaces is the development of tunability. Herein, the techniques and development of applications of tunable metasurfaces are presented through the incorporation of active materials and controllable external stimuli, and the uncovered tunable characteristics are critically analyzed. The review rounds up by proposing the future directions and prospects for actively tunable metasurfaces and their potential practical applications.

Tunable metasurfaces towards versatile metalenses and metaholograms: a review

“…To overcome this limitation, tunable metasurfaces are being developed. 62 Here, we have presented an overview of the recent advances in the design of tunable metasurfaces.…”

“…The nematic phase has a fixed orientation, the smectic phase has a fixed orientation in well-defined planes, and the isotropic phase has random orientations. 62 Therefore, LCs can be used to control the local birefringence, which is used to reconstruct various holographic images by exerting external electric fields.…”

“…Tunable metasurfaces with multiple functionalities through the active control of electromagnetic waves have been actively studied. 61,62 Tunable metasurfaces are made up of metaatoms that are controlled by external stimuli such as electrical biases or high-intensity light sources. Electrical, thermal, and mechanical stimuli have been used to induce two or more optical responses in single-or double-layered metasurfaces.…”

Metasurface-empowered spectral and spatial light modulation for disruptive holographic displays

“…To achieve active tuning of the optical properties, active materials exhibiting several responses under external stimuli have been integrated with metasurfaces and received a lot of attention. 154,155 Tunable metasurfaces that can reconstruct different holographic images through external electrical, chemical, thermal, and mechanical stimuli have been demonstrated. In this section, we will discuss the methods and provide examples of tunable metaholograms, which are classified according to the type of external stimulus.…”

Next-Generation Imaging Techniques: Functional and Miniaturized Optical Lenses Based on Metamaterials and Metasurfaces

“…Propagation of light is determined by the geometrical structure, dimensions and arrangement of the subwavelength-scale constituents of the metamaterials. Thus, appropriately-designed metamaterials offer unprecedented abilities to control the properties of light, including trajectory, wavefront, polarization and phase [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Naturally, metamaterials and metasurfaces have been evaluated as replacements for conventional lenses to focus light [18,19].…”