Active metamaterials and metadevices: a review

Abstract

Metamaterials, as artificially structured materials composed of subwavelength arrays of resonant unit cells, can exhibit exotic properties beyond those accessible to natural materials. They were initially proposed for challenging fundamental laws and demonstrating negative refraction in the microwave regime, and subsequently exploited as a versatile platform to manipulate electromagnetic waves throughout the spectrum via their extreme scalability. Over the past decade, research into metamaterials has been extended to a search for real-world applications, leading to the concept of metadevices, defined as metamaterial-based devices that can operate in an active manner. Due to their subwavelength scale, metamaterials present intriguing strategies for active tuning and provide flat, high-efficiency alternatives to conventional optical systems based on bulky components. In this topical review, we summarize the development of active metamaterials and metadevices ranging from microwave to visible wavelengths, including milestones as well as the state of the art. We survey tuning strategies based on mechanical reconfiguration and incorporation with active materials such as varactor diodes, semiconductors, liquid crystals, phase change materials, superconductors, and two-dimensional materials under various external stimuli, and discuss their fascinating advantages and potential challenges to be confronted. Finally, future prospects together with several emerging tuning strategies and materials are presented at the end.

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

“…Metamaterial is a kind of composite material with an artificial structure [22][23][24]. With the development of metamaterials, researchers have found that the concept of metamaterials can be used to design superconductors and a metamaterial superconductor can exhibit a higher T C [25][26][27][28][29][30]. In 2007, our group doped inorganic electroluminescence (EL) material in a superconductor to increase T C via EL.…”

Sensing of Surface and Bulk Refractive Index Using Magnetophotonic Crystal with Hybrid Magneto-Optical Response

“…Another possibility to increase the resonance Q-factor is to introduce a magnetic material in the sensing structure and to utilize the magneto-optical measurements of the transverse magneto-optical Kerr effect (TMOKE) instead of optical reflectance spectra [ 5 , 19 , 20 , 21 , 22 ]. The magneto-optical response can be enhanced with a variety of metamaterials [ 23 , 24 , 25 , 26 ], plasmonic coatings, dielectric nanostructures [ 27 , 28 , 29 ], and photonic crystals [ 30 , 31 , 32 , 33 ].…”

Sensing Enhancement of Electromagnetically Induced Transparency Effect in Terahertz Metamaterial by Substrate Etching

“…In recent years, the trends of metamaterial research have progressed toward the realization of particular functions by constructing customized metasurfaces to control its optical properties [1][2][3][4][5], thereby creating extraordinary opportunities in the field of various functional devices like modulators, absorbers, and sensors [6][7][8][9]. Recently, researchers have shown an increased interest in the electromagnetically induced transparency (EIT) phenomenon in metamaterials, which is actually a quantum interference effect that forms a narrow transparent window within a broad absorption spectral region in multiple-level atomic systems [10][11][12][13][14][15].…”