Xinhua News Agency reported that a terahertz chip the size of a grain of rice can play a huge role in the human body security checker. The reporter learned from China Electronics Technology Group on the 23rd that the first domestic terahertz imaging chip developed by China Electronics 13 was officially released at the first Digital China Construction Summit. Since the terahertz wave signal radiated by the human body itself is extremely weak, the terahertz chip is required to have ultra-high sensitivity, ultra-low noise and ultra-broadband characteristics in order to detect the weak signal radiated by the human body, so as to achieve the purpose of imaging
太赫兹 编辑
Terahertz (Tera Hertz, THz) is one of the fluctuation frequency units, also known as terahertz, or terahertz. Equal to 1,000,000,000,000Hz, commonly used to denote the frequency of electromagnetic waves. Terahertz is a new radiation source with many unique advantages; Terahertz technology is a very important cross-cutting frontier field, providing a very attractive opportunity for technological innovation, national economic development and national security. [1]
Chinese name Terahertz foreign name terahertz
Abbreviated as THz, the substantial frequency unit is used to express the frequency of electromagnetic waves.
content
1 历史
2 定义
3 特点
4 应用
5 前景
6 技术突破
In the early days, terahertz had different names in different fields. In the field of optics, it was called far-infrared, and in the field of electronics, it was called sub-millimeter wave, ultra-microwave, etc. Before the mid-1980s, the development of infrared and microwave technologies on both sides of the terahertz band was relatively mature, but people's understanding of the terahertz band was still very limited, forming the so-called "THz Gap". In 2004, the U.S. government rated THz technology as one of the "Top Ten Technologies that Change the World in the Future", while Japan listed THz technology as the first of the "Top Ten Key Strategic Objectives of the National Pillar" on January 8, 2005. Raise the strength of the whole country for research and development. The Chinese government specially held the "Xiangshan Science and Technology Conference" in November 2005, inviting a number of domestic academicians who are influential in the field of THz research to discuss the development direction of my country's THz cause and formulate a development plan for my country's THz technology. At present, a number of domestic research institutions have carried out related research in the field of terahertz. Among them, Capital Normal University started earlier and invested more. In terms of terahertz spectroscopy, imaging and identification of drugs and explosives, the use of terahertz to A lot of pioneering work has been done in the non-destructive testing of internal defects of non-polar aerospace materials. At the same time, due to the unique advantages of terahertz rays in safety inspection, the terahertz laboratory of Capital Normal University is focusing on research and development that can be used for real-world testing. Security check prototype device. In addition, many governments, institutions, enterprises, universities and research institutions in the United States, Europe, Asia, Australia and other countries and regions have invested in the research and development boom of THz. One of the pioneers in the field of THz research, Dr. Zhang Xicheng, a famous American scholar, said: "Next ray, T-Ray!". Definition Edit THz waves (THz waves) contain electromagnetic waves with frequencies from 0.1 to 10THz. The term applies to electromagnetic radiation from frequencies between the high-frequency edge of the millimeter-wave band (300 GHz) and the low-frequency far-infrared spectral band edge (3000 GHz), the corresponding wavelengths of radiation in this frequency band range from 0. 03mm to 3mm (or 30~3000μm). The reason why people pay attention to THz technology is that THz rays are ubiquitous and are effective clues and tools for people to understand nature. However, compared with electromagnetic waves in other bands such as infrared and microwave, its understanding and application are very lacking. Second, THz rays have their own characteristics. The typical pulse width of THz pulses is in the order of picoseconds, which not only facilitates time-resolved research, but also effectively suppresses the interference of far-infrared background noise through sampling measurement technology. At present, pulsed THz radiation usually has a low average power of THz rays, but because of the high peak power of THz pulses and the use of coherent detection techniques to obtain the real-time power of THz pulses rather than average power, there is a high degree of confidence. noise ratio. Currently, the signal-to-noise ratio in time-domain spectroscopy systems can reach 10^5 or higher. THz pulse sources usually contain only a few cycles of electromagnetic oscillations, the frequency band of a single pulse can cover the range from GHz to tens of THz, the vibrational and rotational energy levels of many biological macromolecules, dielectrics, semiconductor materials, superconducting materials, and thin-film materials. The phonon vibrational energy levels of etc. fall in the THz band range. Therefore, THz time-domain spectroscopy, as an effective means to detect the information of materials in the THz band, is very suitable for measuring the absorption spectrum of materials and can be used for qualitative identification. The energy of THz photons is low, and the energy of photons with a frequency of 1THz is only about 4 millielectron volts, so it is not easy to destroy the detected material. Many non-metallic and non-polar materials have small absorption of THz rays, so it is possible to detect the internal information of the material by combining with the corresponding technology. For example, ceramics, cardboard, plastics, foam, etc. are transparent to THz electromagnetic radiation, so THz technology can be used as a non-ionizing and coherent complementary radiation source for x-rays for security monitoring in airports, stations, etc., such as exploration Concealed smuggled items include firearms, explosives, and drugs, as well as for detection of integrated circuit soldering conditions. Polar substances have strong absorption of THz electromagnetic radiation, especially water. Various measures should be taken to avoid the influence of moisture in THz spectroscopy technology. In imaging technology, this feature can be used to distinguish different states of biological tissues, such as the distribution of fat and muscle in animal tissues, to diagnose the degree of damage to burn sites in humans, and the distribution of water content in plant leaf tissues. Compared with imaging technologies in other bands, terahertz imaging technology has significantly increased the resolution and depth of field of the detected images (ultrasound, infrared, and X-ray technologies can also improve image resolution, but millimeter-wave technology does not. no significant improvement). In addition, terahertz technology has many unique properties, such as less scattering in inhomogeneous materials, the ability to detect and measure water vapor content, and so on. Terahertz spectroscopy technology not only has a high signal-to-noise ratio, it can quickly analyze and identify subtle changes in sample composition, but also terahertz spectroscopy technology is a non-contact measurement technology that enables it to measure the physical properties of semiconductors, dielectric thin films and bulk materials. information for fast and accurate measurements. In view of the characteristics of THz rays, it will definitely bring far-reaching influences to the fields of communication, radar, astronomy, medical imaging, biochemical identification, materials science, security inspection, etc., and then change people's production and life. Application editing Terahertz imaging technology and terahertz spectroscopy thus constitute the two main key technologies for terahertz applications. At the same time, because the terahertz energy is very small, it will not cause damage to the material, so it has more advantages compared with X-rays. THz time-domain spectroscopy technology has already begun commercial operation, and many companies around the world have begun to produce commercial THz time-domain spectrometers, mainly from China, the United States, Europe and Japan. The basic principle of THz time-domain spectroscopy is to use femtosecond pulses to generate and detect time-resolved THz electric fields, and obtain spectral information of the object to be measured through Fourier transform. Since the vibration and rotation energy levels of macromolecules are mostly in the THz band, and , especially biological and chemical macromolecules are material groups with their own physical properties, and then the material structure and physical properties can be analyzed and identified through characteristic frequencies. One of the more important applications can be drug quality supervision. Imagine that a THz time-domain spectrometer is installed on the assembly line of a pharmaceutical factory, and each piece of medicine from the pharmaceutical factory is spectrally measured and compared with the standard medicine. Inferior tablets are removed to avoid quality differences between different tablets or different batches of tablets, and to ensure the quality of medicines. THz imaging technology Like imaging technologies in other wavelength bands, THz imaging technology also uses THz rays to irradiate the object to be measured, and obtains information about the sample through the transmission or reflection of the object, and then image. THz imaging technology can be divided into two types: pulsed and continuous. The former has the characteristics of THz time-domain spectroscopy technology. At the same time, it can perform functional imaging of matter groups and obtain the refractive index distribution inside the matter. For example, sunflower seeds can and easily obtain the internal information of sunflower seeds. Figure 3-4 shows the actual photo of the sunflower seed sample and the THz transmission image reconstructed by the corresponding method, which can clearly distinguish the outline of the husk and the shape of the kernel hidden in the husk, which is the most hopeful. Likewise, if the sample is a human tooth, the normal part of the tooth will be easily distinguished from the decayed part, and at the same time, X-rays do not have to be irradiated, and there is no additional damage to the human body. Security inspection The use of security inspection should be said to be the most attractive THz technology at this stage. Its essential principle is THz imaging. At present, it mainly uses continuous wave THz sources, and because it needs to solve the most concerned anti-terrorism technology. , anti-drug and other issues that attract the most attention, so they are listed separately. At present, the THz security inspection equipment developed in the UK has entered the trial stage. Due to the penetrability of THz rays and the strong reflection characteristics of metal materials, and the high frequency of THz makes the imaging resolution higher, it is easy to see items such as knives and firearms hidden in clothing and shoes. At the same time, if combined with the substance identification characteristics of THz, it can distinguish whether you are carrying explosives or drugs. The THz Laboratory of Capital Normal University has established a database of common explosives and drugs. It is conceivable that in a few years, real THz security inspection equipment can be seen at the airport. In addition, suicide bombing terrorist attacks that cause social unrest around the world can also be prevented by using THz security inspection equipment. Because the guards can no longer be soldiers or security personnel, but THz security scanners, people do not need to be close to suspicious elements to check them. THz radar In fact, it is also a kind of imaging. In view of the strong absorption of THz rays by moisture in the atmosphere, short-range radar is the advantage of THz rays. A very desirable application is through-wall radar and mine detection radar. Of course, it can also be used for the search and rescue of victims in earthquake relief. It is still in the research and development stage. This is because the walls, wood and other materials pass through THz, while the human body contains a lot of water and does not pass through THz. Therefore, the distribution and activities of people in the house can be detected through the walls, which will have a profound impact on anti-terrorism and anti-kidnapping. The same can also be used to find the human body under the ruins. The mine detection radar is because mines are generally on or near the surface, and dry soil can transmit THz rays, and mines will reflect the THz rays back, so that the target can be found. Astronomy In the universe, a large amount of matter is emitting THz electromagnetic waves. A large number of molecules such as carbon (C), water (H2O), carbon monoxide (CO), nitrogen (N2), and oxygen (O2) can be detected in the THz frequency band. Before the application of THz technology, some of these substances could not be detected at all, and the other part could only be detected at high altitudes or on the surface of the moon. Communication technology THz can be used for communication to achieve a wireless transmission speed of 10GB/s, especially satellite communication. Because in outer space, in a state of approximate vacuum, the influence of moisture does not need to be considered, which is hundreds to thousands faster than the current ultra-broadband technology. multiple times. This enables THz communication to carry out high-security satellite communication with extremely high bandwidth. Although it cannot be commercialized in the communication field due to the lack of efficient THz transmitting antennas and sources, it will be solved by new transmitting devices and sources. Terahertz radiation German researchers have used supercomputer calculations to find that using intense terahertz radiation, it is possible to instantly boil a tiny amount of water in less than a trillionth of a second. Terahertz radiation refers to the electromagnetic radiation region with frequencies ranging from 0.1 terahertz to 10 terahertz and wavelengths between millimeter waves and infrared rays. One terahertz equals one trillion hertz. The German Electron Synchrotron Institute reports that intense terahertz radiation can cause water molecules to vibrate violently, breaking the hydrogen bonds between water molecules. This method heats about a nanoliter (one billionth of a liter) of water to 600 degrees Celsius in half a picosecond (a picosecond is one trillionth of a second). The report notes that one nanoliter of water, while not much, is sufficient for many experiments. A picosecond is much faster than the blink of an eye, so this method of boiling water is arguably the fastest ever. Although this "boiling water" method has not yet been put into practice, the researchers say that water plays an important role in many chemical and biological processes, and the new discovery may provide more experimental possibilities in the field of chemistry and biology. [2] Academician Du Xiangwan, academician of the Chinese Academy of Engineering in Biomedicine, pointed out that among all physical technologies, electromagnetic wave technology has a particularly prominent role in promoting medicine. Since X-ray won the first Nobel Prize in Physics in 1901, five Nobel Prizes related to biomedicine have been awarded to the field of X-ray spectroscopy. In the application of terahertz technology in biomedicine, the interaction of biological macromolecules is the key cause of major life phenomena and lesions, and the energy of terahertz photons covers the energy level range of the spatial conformation of biological macromolecules. This frequency band contains important information such as the spatial conformation that directly represents the function of biological macromolecules that cannot be detected by other electromagnetic bands. Therefore, it is possible to develop a new theory and new technology using terahertz to detect and intervene in the interaction process of biological macromolecules, and provide advanced technical means for the diagnosis and effective intervention of current major diseases. Li Zeren, a researcher from the Institute of Fluid Physics, Chinese Academy of Engineering Physics, also said that through the country's strong support for key technologies and equipment such as terahertz sources, detectors, and imaging systems, my country has basically had the foundation for terahertz biomedical research. [3] Others In addition, terahertz is also widely used in the research of properties of semiconductor materials and high-temperature superconducting materials. Studying this frequency band will not only drive significant advances in theoretical research work, but will also pose significant challenges to solid-state electronics and circuit technology. At present, generally speaking, the research of THz technology mainly focuses on three major contents, THz generation source, THz detection and application research. The biggest difficulty at present is that there is no high-power portable continuously adjustable low-cost THz emission source and optical filters that meet practical requirements, and there is no passive detector that can directly detect THz rays at room temperature. Prospect Editing The unique properties of terahertz give communications (broadband communications), radar, electronic countermeasures, electromagnetic weapons, astronomy, medical imaging (label-free genetic inspection, imaging at the cellular level), non-destructive testing, security inspection (biochemical inspection) and other fields have had a profound impact. Because of the high frequency of terahertz, its spatial resolution is also high; and because its pulse is very short (on the order of picoseconds), it has high temporal resolution. Technological breakthrough[edit] On October 28, 2016, the 23rd Institute of China Aerospace Science and Industry Corporation has obtained China's first terahertz band field SAR image, and the key technology of terahertz band radar imaging has achieved breakthrough results. Through the first terahertz field SAR image, the main technical indicators and imaging algorithms have been tested and verified, laying a technical foundation for the application of terahertz radar engineering. However, due to the limitation of the development level of high-power terahertz radiation sources, the imaging of terahertz radar systems cannot fully meet the needs of practical applications. [4]