Recent Advances in Tunable Metasurfaces and Their Application in Optics

Abstract

Metasurfaces can be opportunely and specifically designed to manipulate electromagnetic wavefronts. In recent years, a large variety of metasurface-based optical devices such as planar lenses, beam deflectors, polarization converters, and so on have been designed and fabricated. Of particular interest are tunable metasurfaces, which allow the modulation of the optical response of a metasurface; for instance, the variation in the focal length of a converging metalens. Response tunability can be achieved through external sources that modify the permittivity of the materials constituting the nanoatoms, the substrate, or both. The modulation sources can be classified into electromagnetic fields, thermal sources, mechanical stressors, and electrical bias. Beside this, we will consider optical modulation and multiple approach tuning strategies. A great variety of tunable materials have been used in metasurface engineering, such as transparent conductive oxides, ferroelectrics, phase change materials, liquid crystals, and semiconductors. The possibility of tuning the optical properties of these metamaterials is very important for several applications spanning from basic optics to applied optics for communications, depth sensing, holographic displays, and biochemical sensors. In this review, we summarize the recent progress on electro-optical magnetic, mechanical, and thermal tuning of metasurfaces actually fabricated and experimentally tested in recent years. At the end of the review, a short section on possible future perspectives and applications is included.

Dual-Band All-Optical Logic Gates by Coherent Absorption in an Amorphous Silicon Graphene Metasurface

“…Optical logic gates, the fundamental element of optical computing, have attracted much attention due to their ultrahigh process speed, high information capacity, and low power consumption [ 1 , 2 , 3 ]. Metamaterials and their two-dimensional (2D) equivalents metasurfaces, are the artificial metal or dielectric structures that can manipulate the amplitude, phase, and polarization of electromagnetic waves in the subwavelength scale [ 4 , 5 , 6 , 7 ], which have been applied in a wide range of fields, including negative refraction [ 8 ], beam steering [ 9 ], holography [ 10 ], perfect absorption effect [ 5 ], sensing [ 6 ], etc. With the development of nanotechnology, metamaterials and metasurfaces have been used to realize optical logic gates for their advantages of integrability, broad operation bandwidth, and ability to manipulate light in the subwavelength scale [ 11 , 12 , 13 ].…”

A Low Profile Wideband Linear to Circular Polarization Converter Metasurface with Wide Axial Ratio and High Ellipticity

“…Polarization is a fundamental characteristic of electromagnetic waves (EMW) with many applications in the microwave, millimeter wave, and optical fields [1][2][3][4][5]. Controlling the polarization state of electromagnetic waves is of great importance.…”