THz Research and Development Network Around China First Station
Capital Normal University

Source: China THz Research and Development Network (CTRDN)  JoJo Ma and Yang Ping

    2. Achievements in Labs

    The THz Lab in Capital Normal University is specialized in the research of THz spectrum and imaging. With years of experience and development, the lab has made great success in drug inspection, explosive spectrum and imaging. The innovative production and technique related have been expanding into other relevant fields.

    Research Direction No. One: Research on THz spectrum

    It is focused on the THz spectrum research of explosives, drugs and biological particles.

    Due to the important role of security inspection and environmental control of explosives, the THz spectrum and imaging is emphasized in the current research. Many of the explosive molecules vibrate in the range between 100G-10THz, which found between the microwave and infrared range. With the application of THz-TDs technology, the characteristic spectrum of those materials can be obtained so that the internal structure information can be analyzed. This process is one of the important parts of THz optics spectrum research as well as the premises to recognize the dangers in environment controlling.

    Drug problem is one of difficult issues puzzling the world. Similar to explosives, many of the drug molecules also vibrate in the range between 100G-10THz. Therefore, it is possible to set up the drug spectrum database by accumulating the fingerprint THz spectrum of drugs in order to distinguish different drugs.

    THz radiation can be applied in the detection of medicine and biological molecules as well as disease diagnosis. With the direct inspection of gene substance (such as DNA or RNA) integration, genetic analysis and unmarked testing of technological chip technology can be realized. Besides, with the water content and distribution inspection of organism, it is possible to distinguish the healthy tissues from the pathologically changed tissues. Furthermore, with the different responses to THz radiation, the map to record and distinguish the healthy and abnormal tissues can also be drawn. As to the THz spectrum of biological molecules in the lab, the first step is the THz¡ªTDS spectrum testing and theoretical simulation of protein and amino acid and related ramification

    Research Direction No. Two: Research on THz image

    The lab is engaged in optics-based THz impulse production and exploration technology, electronics-based THz continuum wave production and exploration technology, impulse and continuum wave THz imaging technology and strategy, as well as THz imaging recognition, image processing theories and algorithm.

    The research includes£º

    (a)Optics-based THz impulse imaging and recognition technology. Two aspects are related in the research, i.e. THz impulse imaging recognition system and image target recognition and identification algorithm.

    (b)Electronics-based THz continuum wave imaging recognition technology.

    Research Direction No. Three: THz and infrared undamaged inspection

    Foam and plastic materials used in aviation usually has a low absorptive and refractive rate in the range of THz wave band. Therefore, THz wave can perforate the foam material even inches¡¯ thick as well as inspect the defects inside. THz inspection and image processing technology are the focus of this research.

    Infrared heat wave inspection technology is one the newly developed undamaged inspection technology which may enjoy a bright future. The basic theory is to take the advantage of the inter-relationship between the tested materials and changeable temperature field(heating controlling). By investigating the surface temperature diversification of the materials, the internal structure and defect information can be obtained. One thing that needs to mention is that the application of wave heat theory and active controlling heating together with infrared undamaged inspection technique is totally different from the traditional passive infrared imaging inspection.

    Comparatively speaking, infrared heat imaging technology is a well-developed technology. Due to the fact that the infrared wave band of electromagnetic radiation is closely next to THz wave band, the THz imaging technology will use infrared imaging technology for reference. At the same time, both methods will be developed in the process of their mutual borrowing, corroborating and complementing.

    Research Direction No. Four: THz transmission and substance inter-reaction

    THz transmission research

    In THz wave band, a high permittivity can be obtained and the absorbing capacity of the substance is close to zero. Therefore, the localization effect of 3D Random Medium can be easily observed in THz wave band. THz provides an ideal research platform for multi-dispersion and  electro-magnetic diffraction research. In fact, all these problems concerned are frequently involved in the fields of medical optics, geophysics and physics, etc. With the spatial resolution of sub-wavelength and temporal resolution of sub-cycle, THz is able to distinguish the plural wave surface as well as the direct statistic research on radioactive field.

    Atmosphere science research

    Collision: particles in atmosphere collide at the picosecond, or trillionth of a second, timescale, which enables THz to be the best method in this research.

    Quanta collision under interstellar temperature: particle collision will appear totally different at super-low temperature (less than 10K) because with the room temperature, there are many collision channels so that the collision sections change at a very low speed. However, with the extremely low temperature, the distance between collision energy and rotation level can be assimilated so that the collisions have the obvious characteristics of quantum mechanics such as sympathetic vibration occurred near the collision section.

    Gas phase Kinetics: It is a dream in the future considering THz provides such a good method for many fields. After all, the time measurement of these processes depends on pressure. The quasi-continuous THz wave technology (impulse wavelength is at millisecond scale) is an ideal tool for the future research.

    Single cycle impulse£­Linear and Nonlinear research of optic features:

    In THz wave band, it is easy to obtain the swing with high resolution and detailed phase information. With the application of THz strong impulse, nonlinear optic research can be carries out. Therefore, THz technology used in the research of single cycle impulse is very significant. Theoretically speaking, non-slowly-varying envelope can be applied for all the research concerned with2-order and 3-order nonlinear optics phenomena. Therefore, it is a brandly new research field for non-linear optics.

    There are dozen of projects in THz field applied by this lab for the past three years, which include tasks that belong to National 836 Project, National 973 Project, the sub-tasks of National Natural Science Fund Key Project, Overall Arming Key Projects, National Natural Fund Covered tasks, and provincial projects (including the key projects organized by Beijing Municipality Education Committee. )

    There are more than 100 academic papers published by the group in the important magazines and journals like Phys. Rev. Lett., Appl. Phys. Lett. Opt. Lett. This lab is also in charge of the sub-tasks sponsored by the National Science Fund Key Project, National 836 Project, Overall Arming Key Projects Fund, etc. which amounted to 15 projects. Besides, 30 postgraduates were trained and 11 patents were authorized.