Graphene-Based Tunable Metamaterial-FSS RAS

Abstract

Metamaterials (MMs) are periodic and/or non-periodic subwavelength structures with a unique response to electromagnetic (EM) waves compared to conventional materials. MMs possess negative permittivity and/or permeability; the combination of both negative is not found in conventional materials. The shape, dimensions, and materials used in the MM determine its ultimate working frequency and response. Owing to their peculiar properties, MMs have found new-age applications such as cloaking, perfect absorber, hyperlenses, modulators, holography, etc. Graphene is a remarkable material with distinctive properties, including excellent thermal and electrical conductivity, very high mechanical strength, along with having a zero bandgap. Further, one of the most important properties of graphene, which has enabled it to be widely used as/along with MMs, is its tunable response to EM waves via a change in conductivity when its chemical potential is varied by applying a bias or doping. Frequency selective surfaces (FSSs), or flat MMs, and MMs utilizing graphene, find applications for defense and security systems in infrared, terahertz, and microwave frequency range. The broad areas of application include stealth, communications, and imaging. Stealth applications aim to prevent radar detection by absorbing or dissipating the incoming EM waves using graphene MMs or FSSs [which act as radar absorbing surfaces (RASs)]. Another important stealth application, although a futuristic one, is cloaking. Fast, secure, and high volume data transfer is critical for any security system, and graphene MMs can improve upon the existing technologies, particularly in the terahertz frequency range. Graphene MMs can be used to develop lenses, mirrors, hyperlenses, modulators, etc., for infrared (thermal) and terahertz imaging systems. In the current chapter, the basic properties of graphene, the working of FSSs and RASs, and applications of graphene-based MMs in defense and security systems are discussed.