Metamaterial absorber

A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics. A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics. For practical applications, the metamaterial absorbers can be divided into two types: narrow band and broadband. For example, metamaterial absorbers can be used to improve the performance of photodetectors. Metamaterial absorbers can also be used for enhancing absorption in both solar photovoltaic and thermo-photovoltaic applications. Skin depth engineering can be used in metamaterial absorbers in photovoltaic applications as well as other optoelectronic devices, where optimizing the device performance demands minimizing resistive losses and power consumption, such as photodetectors, laser diodes, and light emitting diodes. In addition, the advent of metamaterial absorbers enable researchers to further understand the theory of metamaterials which is derived from classical electromagnetic wave theory. This leads to understanding the material's capabilities and reasons for current limitations. Unfortunately, achieving broadband absorption, especially in the THz region (and higher frequencies), still remains a challenging task because of the intrinsically narrow bandwidth of surface plasmon polaritons (SPPs) or localized surface plasmon resonances (LSPRs) generated on metallic surfaces at the nanoscale, which are exploited as a mechanism to obtain perfect absorption. Interest in metamaterials is a result of their flexibility when interacting with and controlling electromagnetic radiation such as light. These are optical materials that can function in a manner similar to glass or prisms. However, these materials extend the capability to control the electromagnetic radiation that flows through them. Also the manner of control is different and new. With conventional materials the way to alter them is to add a chemical or material such as traces of lead added to glass. In contrast, it is the spacing and shape of a given metamaterial's components that define its use and the way it controls electromagnetic radiation. Unlike most conventional materials, researchers in this field can physically control electromagnetic radiation by altering the geometry of the material's components. Also, metamaterials have successfully interacted in electromagnetic bands across the spectrum from radio frequencies, to microwave, terahertz, across the infrared spectrum and almost to visible wavelengths. 'An electromagnetic absorber neither reflects nor transmits the incident radiation. Therefore, the power of the impinging wave is mostly absorbed in the absorber materials. The performance of an absorber depends on its thickness and morphology, and also the materials used to fabricate it.' 'A near unity absorber is a device in which all incident radiation is absorbed at the operating frequency–transmissivity, reflectivity, scattering and all other light propagation channels are disabled. Electromagnetic (EM) wave absorbers can be categorized into two types: resonant absorbers and broadband absorbers. A metamaterial absorber utilizes the effective medium design of metamaterials and the loss components of permittivity and magnetic permeability to create a material that has a high ratio of electromagnetic radiation absorption. Loss is noted in applications of negative refractive index (photonic metamaterials, antenna systems metamaterials) or transformation optics (metamaterial cloaking, celestial mechanics), but is typically undesired in these applications. Complex permittivity and permeability are derived from metamaterials using the effective medium approach. As effective media, metamaterials can be characterized with complex ε(w) = ε1 + iε2 for effective permittivity and µ(w) = µ1 + i µ2 for effective permeability. Complex values of permittivity and permeability typically correspond to attenuation in a medium. Most of the work in metamaterials is focused on the real parts of these parameters, which relate to wave propagation rather than attenuation. The loss (imaginary) components are small in comparison to the real parts and are often neglected in such cases.