Underused part of the electromagnetic spectrum gets optics boost from metamaterial

July 14, 2020

Terahertz radiation, or T-rays, 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.

The findings are published in the peer-reviewed journal Optics Express on July 13th, 2020.

The 'terahertz gap' is a term used by engineers to describe how very little technology exists that makes use of the frequency band in the electromagnetic spectrum that lies between microwaves and infrared radiation: terahertz radiation (also called T-rays).

While it is straightforward to generate and manipulate microwaves and infrared radiation, practical technologies that operate at room temperature and that are able to do the same with T-rays are inefficient and impractical.

This is a great shame, as the properties of T-rays would make them extremely useful if we could indeed harness them.

T-rays can penetrate opaque objects like X-rays, but they are non-ionizing, so much safer. They can also go through clothing, wood, plastics, and ceramics, so are of interest for the security and surveillance sector for real-time imaging to identify concealed guns or explosives. For this same reason, terahertz radiation applications are also promising for cultural heritage science, offering art historians and museums a no-radiation risk option for investigation of artifacts ranging from paintings to mummies.

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 Associate Professor and 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--a device that narrows beams or waves, typically consisting of a curved lens or mirror--that can manipulate T-rays is a bulky three-dimensional structure made of naturally occurring materials.

But the TUAT researchers, Takehito Suzuki, Kota Endo, and Satoshi Kondoh, have devised a collimator as an ultra-thin (2.22 micrometers) plane made from a 'metasurface'--a material that is engineered to have properties that are impossible or difficult to find in nature. 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 (how slow light travels through it) and low reflectance (proportion of light reflected after striking a surface). 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."
-end-
This research was supported by Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (JSPS) (18K04970), PRESTO from the Japan Science and Technology Agency (JST) (JPMJPR1815), TEPCO Memorial Foundation, and Inamori Foundation.

For more information about the Suzuki laboratory, please visit http://web.tuat.ac.jp/~suzuki-lab/index-e.html, http://web.tuat.ac.jp/~suzuki-lab/index.html

About Tokyo University of Agriculture and Technology (TUAT):

TUAT is a distinguished university in Japan dedicated to science and technology. TUAT focuses on agriculture and engineering that form the foundation of industry, and promotes education and research fields that incorporate them. Boasting a history of over 140 years since our founding in 1874, TUAT continues to boldly take on new challenges and steadily promote fields. With high ethics, TUAT fulfills social responsibility in the capacity of transmitting science and technology information towards the construction of a sustainable society where both human beings and nature can thrive in a symbiotic relationship. For more information, please visit http://www.tuat.ac.jp/en/.

Contact:

Takehito Suzuki, Ph.D.
Associate Professor,
Institute of Engineering,
Tokyo University of Agriculture and Technology, Japan
E-mail : takehito@go.tuat.ac.jp

Yuko Shimabayashi
Department of Strategic Basic Research,
Japan Science and Technology Agency (JST)
E-mail: presto@jst.go.jp

Tokyo University of Agriculture and Technology

Related Terahertz Radiation Articles from Brightsurf:

Terahertz receiver for 6G wireless communications
Future wireless networks of the 6th generation (6G) will consist of a multitude of small radio cells that need to be connected by broadband communication links.

A breakthrough in developing multi-watt terahertz lasers
Researchers from Lehigh University are reporting another terahertz technology breakthrough: they have developed a new phase-locking technique for plasmonic lasers and, through its use, achieved a record-high power output for terahertz lasers.

Doing more with terahertz: Simplifying near-infrared spectroscopy systems
Researchers from Beihang University, China, and Tokushima University, Japan, have developed a terahertz spectroscopy scheme that offers outstanding resolution using a single laser.

Terahertz radiation can disrupt proteins in living cells
Researchers from the RIKEN Center for Advanced Photonics and collaborators have discovered that terahertz radiation, contradicting conventional belief, can disrupt proteins in living cells without killing the cells.

Terahertz radiation technique opens a new door for studying atomic behavior
Researchers from the Department of Energy's SLAC National Accelerator Laboratory have made a promising new advance for the lab's high-speed 'electron camera' that could allow them to 'film' tiny, ultrafast motions of protons and electrons in chemical reactions that have never been seen before.

Nimotuzumab-cisplatin-radiation versus cisplatin-radiation in HPV negative oropharyngeal cancer
Oncotarget Volume 11, Issue 4: In this study, locally advanced head and neck cancer patients undergoing definitive chemoradiation were randomly allocated to weekly cisplatin - radiation {CRT arm} or nimotuzumab -weekly cisplatin -radiation {NCRT arm}.

Record-breaking terahertz laser beam
Terahertz radiation is used for security checks at airports, for medical examinations and also for quality checks in industry.

A trick for taming terahertz transmissions
Osaka University researchers have invented a wireless communication receiver that can operate in the terahertz frequency band.

Researchers generate terahertz laser with laughing gas
Researchers from MIT, Harvard University, and the U.S. Army have built a compact device, the size of a shoebox, that produces a terahertz laser whose frequency they can tune over a wide range.

Terahertz technology escapes the cold
The group of Jérôme Faist in the Department of Physics at ETH Zurich achieved the first realization of a terahertz quantum cascade laser operating without cryogenic cooling.

Read More: Terahertz Radiation News and Terahertz Radiation Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.