Metamaterial
Introduction
Metamaterials are artificial materials engineered to have properties that are not found in naturally occurring materials. They are made from assemblies of multiple elements fashioned from composite materials such as metals and plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement can affect the waves of light or sound in an unconventional manner, creating material properties which are unachievable with conventional materials. These materials are often used in electromagnetic metamaterial antennas and light-matter interactions for beam steering, metamaterial cloaking, superlenses and invisibility cloaking.
History
The concept of metamaterials dates back to the early 20th century, but the term was not coined until 1999 by Rodger M. Walser of the University of Texas. The first effective metamaterial was assembled by David R. Smith's lab at Duke University in 2000. It was a microwave cloak, and it did not render the object invisible to the human eye, but it did show that the microwave signature of the object was reduced. This was a significant step forward in the field of metamaterials.
Types of Metamaterials
There are several types of metamaterials, each with unique properties and uses. These include electromagnetic metamaterials, terahertz metamaterials, photonic metamaterials, tunable metamaterials, frequency selective surface-based metamaterials, nonlinear metamaterials, and chiral metamaterials.
Electromagnetic Metamaterials
Electromagnetic metamaterials manipulate electromagnetic waves to produce effects not achievable with conventional materials. They can affect the reflection, refraction, and transmission of waves. Applications include microwave devices, such as beam steerers and antennas, and optical devices, such as lenses and cloaking devices.
Terahertz Metamaterials
Terahertz metamaterials operate in the terahertz frequency range. They have potential applications in terahertz imaging, terahertz spectroscopy, and terahertz communication systems.
Photonic Metamaterials
Photonic metamaterials affect the properties of light. They can manipulate the refraction, diffraction, and dispersion of light, enabling the creation of devices such as superlenses that can overcome the diffraction limit of conventional lenses.
Tunable Metamaterials
Tunable metamaterials can have their properties changed in real time using external stimuli. This allows for a wide range of applications, including adaptive optics, tunable filters, and switches.
Frequency Selective Surface-Based Metamaterials
Frequency selective surface-based metamaterials are used in antenna design. They can selectively filter certain frequencies while allowing others to pass through.
Nonlinear Metamaterials
Nonlinear metamaterials exhibit nonlinear responses to electromagnetic fields. They can be used to create devices with unique functionalities, such as frequency conversion and phase conjugation.
Chiral Metamaterials
Chiral metamaterials exhibit optical activity and circular dichroism, which can be used in the design of optical devices.
Applications
Metamaterials have a wide range of applications in various fields. They are used in the design of antennas, waveguides, and lenses. They are also used in cloaking devices, superlenses, and other optical devices. In addition, they have potential applications in seismic protection, soundproofing, and medical imaging.
Future Directions
Research in metamaterials is ongoing, with many potential applications yet to be realized. Future directions include the development of more efficient and versatile metamaterials, the exploration of new phenomena and effects, and the application of metamaterials in various fields such as telecommunications, medicine, and defense.