Terahertz (THz) wave refers to the electromagnetic wave with frequency in the range of (0.1-10) THz (wavelength 3000-30 microns), 1thz = 1012hz. It coincides with millimeter wave (submillimeter wave) in the long band, while terahertz wave occupies a special position in the electromagnetic wave spectrum in the short band. THz is located in the special position of electromagnetic spectrum. It has many superior characteristics and has very important academic and application value (some have been in practice), which has attracted great attention all over the world.
Application field of THz technology
THz imaging and THz spectroscopy have very important applications in physics, chemistry, biomedicine, astronomy, material science and environmental science.
1. THz has great attraction in biomedical applications
It has shown its powerful function and effectiveness in the diagnosis and treatment of skin cancer, DNA detection, medical application of THz, THz tomography, biochemical application of THz, drug analysis and detection, etc. Based on the study of protein and gene characteristics, THz biomolecular diagnosis technology can be established. Thus, it greatly promotes the development of molecular biology and has great application prospects in medical treatment and drug development and identification.
2. Because the vibration and rotation frequencies of biological macromolecules are in THz band, and THz radiation technology can extract important information of DNA, THz can play an important role in plant, especially grain seed selection, selection of excellent strains and so on. In short, Terahertz Science and technology is of great significance to agriculture, food processing and other industries. In China, University of Electronic Science and technology, Sichuan Agricultural University, Sichuan Academy of Agricultural Sciences, Ouhua biotechnology and science and Innovation Co., Ltd. of University of Electronic Science and technology jointly applied for the project of introducing plants rich in fruit oligosaccharides using terahertz technology. The project focuses on the determination of terahertz characteristic spectra of fructo oligosaccharides, introduction, breeding and industrialization of snow lotus fruit rich in fructo oligosaccharides. Recently, the project has successfully passed the approval of Chengdu Science and Technology Bureau. This marks a substantial advance in the application of terahertz technology in Sichuan Province and is of great significance to terahertz industrialization.
3. THz radiation can penetrate smoke and detect toxic or harmful molecules, so it can play an important role in environmental monitoring and protection. It is reported that THz environmental monitoring equipment (2.5thz generated by CO2 laser as pump source) has been installed on American satellites.
4. THz has unique advantages in the application of national security and counter-terrorism
Taking advantage of the property that THz can penetrate substances, the UK first developed THz camera and has been tested in airport security inspection, with good results. A company called QinetiQ used a millimeter wave camera to take an image of a fully dressed person, marking hidden guns. Terahertz cameras are considered similar but more useful. Particularly important is the cooperation between the National Laboratory of the United States (ORNL) and the University of Tennessee to carry out the "through the wall program", which uses THz imaging technology to obtain information inside the wall from the outside. Obviously, this through wall technology is of great value in national security. In addition, the use of THz spectrum can quickly and effectively check and identify drugs. The United States has carried out projects such as checking mail with THz spectrum technology, including the detection of THz chemical and biological products. For example, an envelope with white powder seems indeterminate to the naked eye. But with the help of terahertz imaging, postal work can determine whether the packaged powder is stimulant or aspirin. Explosives will be more easily found in luggage.
5. Application of THz in radar and communication
THz also has great potential in radar and communication. There is no doubt that THz has great advantages in space communication. THz radar has special functions in anti stealth. The research work in this field is to prepare for THz radar and so on. THz satellite space imaging and communication technology may be an important area of concern to major powers in the future.
6. THz is applied to the detection of possible faults of space shuttle
Shortly after the Columbia space shuttle crash, based on the video data taken during the launch of the space shuttle, an analysis of the cause of the crash was put forward. An experiment has been carried out in a laboratory in the United States. The center frequency of THz pulse is lthz and the bandwidth is 3thz. After many experiments, especially the recent successful detection of adiabatic foam layer, it is fully proved that THz pulse can indeed carry out effective NDT for space shuttles. China's space development program will certainly need such technology.
7. Terahertz also has astronomical applications
Herschel Space Observatory, a man-made satellite planned to be launched in 2008, is a terahertz version of the Hubble Space Telescope. In Chile, one of the world's largest telescope arrays, Atacama large millimeter wave submillimeter wave interference array (ALMA) is being constructed. It will detect terahertz electromagnetic waves, hoping to find objects in the early days of the universe.
Overview of domestic research
In recent years, terahertz radiation has been widely used in many fields, such as chemistry, physics, medicine and material science. At the same time, the experimental equipment suitable for terahertz radiation has also been widely and rapidly developed. Under the advocacy and promotion of some visionary scientists, such as Chen Jinpei, Du Xiangwan, Liu Shenggang, Yang Guozhen, Yao Jianquan, Zhang Jie, Wu Peiheng and other academicians, China has established a number of terahertz research centers (rooms), promoted the research and development of terahertz technology, and achieved important results. From November 22 to 24, 2005, the 270th symposium with the theme of "new development of Terahertz Science and technology" was held in Xiangshan Hotel, Beijing. So far, China's terahertz research and application development has opened a new stage.
Academician Liu Shenggang suggested to establish a special research plan for terahertz technology at the national level, formulate two five-year plans, increase investment, drive the development of national defense, national security, biomedicine and information through the development of terahertz new technology, enhance China's international status in the terahertz field, and lay a solid foundation for the industrial development of terahertz technology in China.
International developments
At present, a research climax of THz technology has been formed all over the world.
1. Dozens of universities in the United States are engaged in THz research, especially the important national laboratories in the United States are carrying out THz science and technology research. The National Foundation (NSF), the National Space Administration (NASA), the Department of energy (DOE) and the National Institutes of Health (NIH) have made large-scale investment in THz science and technology research since the mid-1990s.
2. Rutherford National Laboratory in the UK, more than a dozen universities such as Cambridge University, Leeds University and Strathclyde, and several universities in Germany are actively carrying out THz research. European countries have also used EU funds to organize large-scale cooperative research projects with multi-disciplinary participation across countries. A special THz research program has been set up in the Russian National Academy of Sciences, and IAP, IGP and some universities are also actively carrying out THz research.
3. In Asian countries and regions, national Seoul University of Korea, POSCO University of science and technology, National University of Singapore, Taiwan University and Taiwan Tsinghua University have actively carried out THz research and published many influential papers.
4. On January 8, 2005, Japan announced Japan's ten-year science and technology strategic plan, put forward ten major key technologies, and listed THz as the first. The University of Tokyo, Kyoto University, Osaka University, Tohoku University, Fukui University and various companies have vigorously carried out the research and development of THz.
