A terahertz metamaterial is a class of composite metamaterials designed to interact at terahertz (THz) frequencies. The terahertz frequency range used in materials research is usually defined as 0.1 to 10 THz. This bandwidth is also known as the terahertz gap because it is noticeably underutilized. This is because terahertz waves are electromagnetic waves with frequencies higher than microwaves but lower than infrared radiation and visible light. These characteristics mean that it is difficult to influence terahertz radiation with conventional electronic components and devices. Electronics technology controls the flow of electrons, and is well developed for microwaves and radio frequencies. Likewise, the terahertz gap also borders optical or photonic wavelengths; the infrared, visible, and ultraviolet ranges (or spectrums), where well developed lens technologies also exist. However, the terahertz wavelength, or frequency range, appears to be useful for security screening, medical imaging, wireless communications systems, non-destructive evaluation, and chemical identification, as well as submillimeter astronomy. Finally, as a non-ionizing radiation it does not have the risks inherent in X-ray screening.
About metamaterials
Currently, a fundamental lack in naturally occurring materials that allow for the desired electromagnetic response has led to constructing new artificial composite materials, termed metamaterials. The metamaterials are based on a lattice structure which mimics crystal structures. However, the lattice structure of this new material consists of rudimentary elements much larger than atoms or single molecules, but is an artificial, rather than a naturally occurring structure. Yet, the interaction achieved is below the dimensions of the terahertz radiation wave. In addition, the desired results are based on the resonant frequency of fabricated fundamental elements. The appeal and usefulness is derived from a resonant response that can be tailored for specific applications, and can be controlled electrically or optically. Or the response can be as a passive material. The development of electromagnetic, artificial-lattice structured materials, termed metamaterials, has led to the realization of phenomena that cannot be obtained with natural materials. This is observed, for example, with a natural glass lens, which interacts with light (the electromagnetic wave) in a way that appears to be one-handed, while light is delivered in a two-handed manner. In other words, light consists of an electric field and magnetic field. The interaction of a conventional lens, or other natural materials, with light is heavily dominated by the interaction with the electric field (one-handed). The magnetic interaction in lens material is essentially nil. This results in common optical limitations such as a diffraction barrier. Moreover, there is a fundamental lack of natural materials that strongly interact with light's magnetic field. Metamaterials, a synthetic composite structure, overcomes this limitation. In addition, the choice of interactions can be invented and re-invented during fabrication, within the laws of physics. Hence, the capabilities of interaction with the electromagnetic spectrum, which is light, are broadened.
Terahertz technology
Terahertz frequencies, or submillimeter wavelengths, which exist between microwave frequencies and infrared wavelengths, are virtually unused in the commercial sector, primarily due are limits to propagating the terahertz band through the atmosphere. However, terahertz devices have been useful in scientific applications, such as remote sensing and spectroscopy.
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