Recent Advances in Tunable Metasurfaces: Materials, Design, and Applications

Abstract

Metasurfaces, a two-dimensional (2D) form of metamaterials constituted by planar meta-atoms, exhibit exotic abilities to tailor electromagnetic (EM) waves freely. Over the past decade, tremendous efforts have been made to develop various active materials and incorporate them into functional devices for practical applications, pushing the research of tunable metasurfaces to the forefront of nanophotonics. Those active materials include phase change materials (PCMs), semiconductors, transparent conducting oxides (TCOs), ferroelectrics, liquid crystals (LCs), atomically thin material, etc., and enable intriguing performances such as fast switching speed, large modulation depth, ultracompactness, and significant contrast of optical properties under external stimuli. Integration of such materials offers substantial tunability to the conventional passive nanophotonic platforms. Tunable metasurfaces with multifunctionalities triggered by various external stimuli bring in rich degrees of freedom in terms of material choices and device designs to dynamically manipulate and control EM waves on demand. This field has recently flourished with the burgeoning development of physics and design methodologies, particularly those assisted by the emerging machine learning (ML) algorithms. This review outlines recent advances in tunable metasurfaces in terms of the active materials and tuning mechanisms, design methodologies, and practical applications. We conclude this review paper by providing future perspectives in this vibrant and fast-growing research field.

Dynamic Chiral Metasurfaces for Broadband Phase‐Gradient Holographic Displays

“…The degree of freedom includes multiple information specifically for metadisplays into a single metasurface with dynamic optical response and integration with external stimuli. [45][46][47] Such dynamic responses are accomplished by phase-change materials (PCMs), [48] such as Vanadium dioxide (VO 2 ) [49,50] and germanium antimony tellurium (GST). [51] However, these materials offer tunability by changing their state from crystalline to amorphous upon applying various electrical and thermal stimuli that eventually vary the material's refractive index (n).…”

Retinal Projection Near‐Eye Displays with Huygens’ Metasurfaces

“…and stimuli (thermal, electrical and optical) have been explored for tunable metasurfaces. [ 50 ] For display application, in particular, electrically tunable metasurface based SLMs working in the visible wavelength range is preferred. [ 40,51–54 ] In the future, this type of devices can be used in displays as dynamic SLMs to encode computer‐generated holograms (CGH).…”

A time-space coding metasurface and potential applications

“…Metasurface, as a two-dimensional version of metamaterial, has demonstrated the fascinating ability to modulate material properties [1]. Since the concept of abrupt phase changes via metasurface was put forward by Yu et al in 2011 [2], metasurface has been widely studied by many scholars and rapidly developed into an artificial structure to meet various needs.…”