Terahertz technology and its application

T-ray is a technique that USES terahertz waves, the so-called terahertz science, to study a segment of an electrical z-wave that can "see through" a lot. More than 100 years ago, terahertz was mentioned in infrared astronomy, but it was rarely touched in scientific research and civil affairs. In the microwave, visible light and infrared technology is widely used, the main reason for the lagging development of terahertz lies in the lack of detector and source, until the recent 10 years, with the improvement of research methods, people in the research of this field has a larger development. At present, the study of terahertz has developed into a new field, and the study of terahertz has grown from three units 20 years ago to more than 200 units worldwide.

Terahertz waves are electromagnetic waves with frequencies ranging from 0.1THz to 10.0THz. It has many outstanding properties and is rated by the United States as one of the "top 10 technologies that will change the world of the future." Terahertz spectroscopy, terahertz imaging and terahertz communication are the three major research directions. It has important applications in many scientific fields such as safety inspection, nondestructive detection, astrophysics, biology, medicine, atmospheric physics, environmental ecology and military science. Schottky diode with high cutoff frequency can realize the mixing, detection and doubling of terahertz waves at room temperature. In addition, the realization of terahertz circuit on low loss substrate is the basis of terahertz technology.

THZ wave is 10 THZ frequency range from 0.1 T to (in 3 mm wavelength to 30 um) of the electromagnetic spectrum, it between millimeter wave and infrared light, so far has not yet been fully human cognition and utilization of spectrum resource, is expected to be on communication (broadband communications, radar, electronic countermeasures, electromagnetic weapons bring profound changes, safety inspection, etc.

Terahertz unique properties for communication (broadband communications, radar, electronic countermeasures, electromagnetic weapons, astronomy, medical imaging (no marker genes of imaging examination, a cellular level), nondestructive testing, safety inspection (biochemical examination), and other fields has brought the profound influence. Because of the high frequency of terahertz, its spatial resolution is also high. It also has a high time resolution because of its short pulse (on the order of picosecond). Terahertz imaging and terahertz spectroscopy are two key technologies for terahertz applications. At the same time, because terahertz is small in energy and does not destroy matter, it has an advantage over x-rays. In addition, because of the biological macromolecules vibration and rotation frequency resonance frequencies are in THZ wave band, so the terahertz in food selection, the choice of fine strains and other agricultural and food processing industry has a good application prospect. The application of terahertz is still in constant development and research, and its vast scientific prospect is recognized worldwide.

After more than a decade of research, the international scientific community has recognized THz science and technology as a very important cross-cutting frontier. THz has a high spatial resolution because of its high frequency (wavelength is more than 1000 smaller than microwave). Because the pulse is short (femtosecond), THz radiation has a high temporal resolution. THz imaging and THz spectroscopy are two key technologies in THz application. On the other hand, the energy of THz is small, it doesn't destroy things, so it has a big advantage over x-rays.

Terahertz cannot replace x-rays, but it has some advantages that x-rays cannot. X-ray and ultrasound can find outline and state of the object, but it cannot detect the chemical properties of the object, unable to distinguish the difference between explosives and drugs, terahertz, however, have the ability, the international fight against terrorism is of great significance. Terahertz has identified more than 50 of the hundreds of types of explosives and mines currently invented by humans. The latest development is around 30 metres, and terahertz is able to spot the explosive accurately. Of course, 30 metres is not a great distance, but it is a valuable asset, unique in comparison to other security measures.

Future terahertz will expand the application scope of the following four aspects, one is the study of the material properties, especially the light molecules and semiconductor, the characteristics of high temperature superconductor research is terahertz spectroscopy application field of another, the second is the THZ imaging and ct imaging technology, three is the research in the field of biological science and medicine, including from a cancer diagnosis to genetic analysis, etc. The latest study found that people often drink coffee if meet with certain drugs, it may become a "poison", and the use of terahertz technology, will be in pharmacology, cancer early diagnosis, etc., likely new breakthrough.

New and powerful new methods of scientific research

(1) THz imaging and THz spectroscopy have extremely important applications in physics, chemistry, biomedical science, astronomy, material science and environmental science.

(2) not only can the THz wave imaging and can serve as a kind of special and effective probe, to conduct the thorough research to the material inside, about physical chemical and biological composition, spectral characteristics, THz markers, quantum interaction process, and other important information.

For example: using the THz research CdSe high temporal resolution optical quantum transition phenomenon, research Ti02 nanometer lattice carrier in the transport process, and research control atoms/molecules no radiation quantum leap, etc are important new results have been achieved. Great achievements have been made in THz quantum optics, quantum computer applications and THz radiation of semiconductors under strong magnetic fields.

Use strong power THz radiation can stimulate the internal material nonlinear dynamics process of atoms and molecules, and thus high power ultrashort pulsed THz can study the nonlinear characteristic of the material at the molecular level.

(3) THz also has important advantages in plasma detection. The spatial distribution of density in high temperature and high density plasma can be detected by THz radiation. THz stands out application in astronomical research, scientists at the South Pole station set up a mobile astronomical, using THz telescopes observed that many important new stars, to study the origin of the universe and the formation of stars has an important significance, it is worth mentioning in early 2005 in China, also established a research station in Antarctic).

THz technology will play an important role in promoting the development of national economy

(1) the application of THz in biomedical science is very attractive. In the diagnosis and treatment of skin cancer, the detection of DNA, the medical application of THz THz imaging fault, THz applied biochemistry, drug analysis and detection, etc, all shows its powerful features and results.

THz biomolecular diagnosis technology can be established based on the study of protein and gene characteristics.

Therefore, it can greatly promote the development of molecular biology, and has a great application prospect in medical treatment and drug research and identification.

(2) due to the rotation frequency of the vibration and biological macromolecules in THz wave band, and the THz radiation technology can extract the important information of DNA, as a result, THz in plants, especially the food selection, the choice of excellent strains can play an important role. In a word, terahertz science and technology is of great importance to agriculture, food processing and other industries.

THz has broad applications in biomedicine. The following figure shows the diagnosis and application of skin cancer in THz.

(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 produced using CO2 lasers as pump sources) has been installed on us satellites.

THz has unique advantages in the application of national security and anti-terrorism

(1) using the property that THz can penetrate substances, the British first developed the THz camera and has been tested in the field of airport security inspection, with good results. In particular, ORNL is working with the university of Tennessee on the Through wall Program, which USES THz imaging to get information from the outside. Obviously, this technique has important value in national security

In addition, the use of THz spectroscopy can quickly and effectively detect and identify drugs. The United States has carried out projects such as the use of THz spectroscopy to check mail, including the detection of THz chemicals and biological products.

(2) THz also has great potential in radar and communications applications. There is no doubt about THz's huge advantage in space communications. THz's atmospheric window has also been studied (figure 6). THz radar has special function in anti-stealth. The following report addresses the problem of high power THz radiation sources, which are prepared for THz radar and others. THz satellite space imaging and communications technology may be important areas of concern for future powers.

(3) THz is used to detect possible failure of the space shuttle

Shortly after the crash of the space shuttle Columbia, an analysis of the causes of the crash was presented based on video footage from the launch of the space shuttle. An American laboratory has conducted experiments. The center frequency of THz pulse is lTHz and the bandwidth is 3THz. Through a number of experiments, especially the recent successful detection of PAL ~ Ramp SOFI insulation foam layer, THz pulse can effectively non-destructive inspection of the space shuttle. Our space program will certainly need such technology.

THz science and technology is the foundation of a new generation of IT industry

(1) scientists expect THz to be highly competitive in modern IT science, technology and industry once THz radiation sources and THz detection technologies are developed. This competition has actually begun.

(2) with the development of THz science and technology, many high-tech companies have been born, for example: the British Rultherford national laboratory (Rutherford Appleton Lab (RAL)) and the European space agency (ESA) in 2002, the executive Star Ti ger after the success of the plan, set up a company ThruVision company, specializing in the work, the commercialization of the THz imaging developed passive THz imaging, has the following characteristics: a. Passive does not require THz source; B. Real-time imaging. The university of Cambridge has spawned TeraView Ltd, a high-tech company called Spinoff. Engaged in the development of THz camera;

(3) Picometrix was incubated in university of Michigen and Stanford university. Physicalscience Inc. ; Calabazas Creek Res. Inc. Companies such as. Picometrix, based in California, is tasked with "handing THz science and technology to government and university LABS so they can be used for research work".

(4) there are also many companies in Japan, which have been engaged in the research, development and commercialization of THz science and technology, including the high-power THz source. IT can be seen that a new generation of IT industry based on THz science and technology has begun to take shape gradually.

The study of THz technology itself is an important subject

Such as the generation mechanism of various THz radiation, propagation and transmission of ultra-short pulse THz, interaction between THz and matter, etc.

Below are some structural block diagrams of THz imaging and THz spectrum. One of them is a 150-micron THz image block diagram developed by JPL. The development and application of THz imaging and THz spectrum can be seen from these block diagrams.

At the same time also can see that in order to establish THz imaging and THz spectrum need to study what THz devices and components, such as: THz sources, THz detection, mixing, THz transmission, resonant, etc., to form a complete system of THz imaging and THz spectrum. From the next section, we will discuss these devices and components.