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| Illustration of a terahertz metasurface ultra-thin collimator for power enhancement. (T. Suzuki, TUAT) |
Terahertz radiation has barely been exploited compared to most of the rest of the electromagnetic spectrum. Yet T-rays potentially have applications in next-generation wireless communications (6G/7G), security systems, biomedicine, and even art history. A new device for controlling T-rays using a specially designed metasurface with properties not found in nature could begin to realize this potential.
Terahertz technology that allows generation, detection, and application of terahertz waves has taken off in the last decade or so, closing the terahertz gap somewhat. But the performance and dimensions of conventional optical components able to manipulate terahertz waves have not kept up with this rapid development. One reason is the lack of naturally occurring materials suitable for the terahertz waveband. However, researchers at Tokyo University of Agriculture and Technology (TUAT) led by terahertz wave engineer Takehito Suzuki have recently developed an optical component that can more easily manipulate T-rays and in a practical fashion by using a material that doesn’t occur in nature.
Conventionally, a collimator, typically consisting of a curved lens or mirror, can manipulate T-rays is a bulky three-dimensional structure made of naturally occurring materials. But the researchers Takehito Suzuki, Kota Endo, and Satoshi Kondoh, have devised a collimator as an ultra-thin (2.22 micrometers) plane made from a metasurface. These properties come not from whatever metal or plastic base substance they are composed of, but instead from the geometry and arrangement of the material in tiny repeating patterns that can bend electromagnetic waves in a way that natural substances cannot.
In this case, the material has an extremely high refractive index and low reflectance. The collimator consists of 339 pairs of meta-atoms arranged so that the refractive index concentrically increases from the outside to the center of the device. “The metasurface design is unprecedented,” said Suzuki, “delivering a much higher performance that should accelerate the development of a wide range of applications, including next-generation wireless communications (6G/7G) and even thermal radiation control devices.” (Source: U. Tokyo)
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