Editor’s note: On September 30, 2021, China Science Daily published on page 3 a signed article by Academician Shenggang Liu and Prof. Min Hu of UESTC, titled “Terahertz: The Untouched Virgin Land of the Information Age”. The full text follows.
In 1865, when the British scientist Maxwell theoretically predicted the existence of electromagnetic waves, he may not have imagined that he was opening an entirely new era for humanity — the information age. In 1888 Hertz first observed electromagnetic waves in experiment, and in 1905 Marconi used them to achieve transoceanic telegraphy. Since then humanity has raced ahead in harnessing electromagnetic waves. From radio to television to wireless communication; from mobile phones and microwave ovens to the Internet and radar — electromagnetic waves are constantly changing our lives. Over the past 150 years, humanity has relentlessly pursued faster, farther and higher-capacity information transmission, a goal that has never ended and never will.
Electromagnetic waves arise from the coupled periodic variation of electric and magnetic fields; the rate of variation is called frequency (in hertz, Hz). Ordered by frequency, they can be arranged along an axis like a family tree — the electromagnetic spectrum. All the waves we use in daily life sit on it; even visible light is an electromagnetic wave, at a frequency of 10^15 Hz.
Humanity understands and exploits most of the spectrum thoroughly — except one band in the middle: the terahertz (THz) band, hailed as the last virgin land of the spectrum, lying in the transition region between electronics and photonics. The terahertz band generally refers to electromagnetic waves from 0.1 to 10 THz, where 1 THz equals 10^12 Hz.
Terahertz waves have high carrier frequency and large bandwidth, enabling huge communication capacity; good penetration and high radar-imaging resolution; low photon energy and high safety, enabling non-destructive testing; and they cover the characteristic spectra of most substances — the so-called fingerprint spectra. These properties give terahertz important value across many fields, making it a commanding height of science and technology contested by nations. The United States has identified terahertz technology as one of the ten technologies that will change the future world; the EU has launched multiple multinational terahertz programs; and Japan ranks terahertz science and technology at the top of its ten-year science and technology strategy.
In fact, terahertz technology is not far from us: the first image of a black hole in 2019 — the famous “doughnut” — was captured with terahertz astronomical telescopes.
Terahertz will also play an important role in future battlefield reconnaissance, stealth and anti-stealth, precision guidance and electromagnetic countermeasures. Victory in future information-based warfare depends on information dominance, whose foundation is control of the electromagnetic spectrum. Terahertz is the last unused spectrum resource: whoever masters it will occupy the commanding heights of future military competition.
Terahertz is also an inevitable choice for future terrestrial wireless communication. Take mobile communication: from 2G to today’s 5G, rates have grown from 200 kb/s to over 100 Mb/s. In the terahertz mobile era, rates will exceed 100 Gb/s — three orders of magnitude higher. One can imagine the changes this will bring. On one hand, the architecture of electronic devices will change revolutionarily, and information exchange will no longer depend on circuit boards and cables. On the other, with ever-growing demand for high-capacity communication, space-based satellite Internet is booming.
Terahertz has shown great potential in high-rate communication, electromagnetic countermeasures, remote sensing, and in frontier fields such as physics, chemistry, biology and medicine. In terahertz-bio interdisciplinary research, for example, infrared spectroscopy detects only the vibrations of molecular bonds, while terahertz can measure the vibrational and rotational spectra of large organic molecular groups composed of carbon, hydrogen, oxygen and nitrogen — such as proteins — revealing molecular-group configurations as fingerprint spectra. In 2014, British scientists first observed in vivo protein folding and showed that proteins can survive for long periods in vitro, opening the door to studying terahertz-biosystem interactions.
China’s formal terahertz research began with the 270th Xiangshan Science Conference. Entrusted by the nation, our team organized experts and scholars at the Fragrant Hill Hotel in Beijing to discuss the direction of terahertz science and technology in China. The consensus was that terahertz is both a “scientific and technological frontier” and a “major national need” — and over time, humanity will make ever fuller use of this band.
Breaking the bottlenecks of terahertz radiation and detection is the core problem to be solved. Their breakthroughs will bring major changes to human life and social development.
Since 2000, terahertz development has passed through several stages: understanding terahertz, developing terahertz components, building demonstration systems, and industrialization. It now stands at the critical transition from demonstration to industrialization. To advance industrialization in four directions — wireless communication, medical devices, biomedical systems and security inspection — a complete innovation chain from fundamental research through components to systems must be established as soon as possible, driving high-quality development of related industries.
This September, the 46th International Conference on Infrared, Millimeter and Terahertz Waves concluded at UESTC. As the oldest and largest top academic conference in the field, held in China for the third time, it fully demonstrates that the “Chinese height” of terahertz research has drawn worldwide attention.
A new round of technological revolution and industrial transformation is advancing rapidly. As scientists, we must keep the nation’s top priorities in mind, strengthen original and leading-edge research, and contribute to high-level self-reliance in science and technology — striving to build China into a global highland of terahertz research.
(Shenggang Liu is an Academician of the Chinese Academy of Sciences and a professor at UESTC; Min Hu is a professor at UESTC.)
China Science Daily (September 30, 2021, page 3, Information Technology)
Report link: http://news.sciencenet.cn/sbhtmlnews/2021/9/365623.shtm
Source: UESTC News (via China Science Daily) Original article