Application Of Terahertz Technology In The Security Check Pre-study

The THz technology is developed with the development of ultra-fast laser in resent years . THz radiation is the gap between microwave and far-infrared region . THz time-domain spectroscopy is a powerful tool developed in 1990s for spectroscopy measurement. This technique can record the amplitude of the wave by electro-optical or photoconductive sampling. After fast Fourier transform , the amplitude and phase of the THz pulse wave is given, then the refractive index and absorption of the material in THz region is extracted.From 1970s,implementing security examination to people pass the important passageway (airport, port, station, custom) has been became common safety precaution all over the world. In recent years, effecting by the queasy situation of the world, public security have became the focus of every government around the world. For Keep away and beat the occurrence and spread of crime, police of every country using new technology of security examination to check dangerous goods or stuff violate a ban. Terahertz has unique attributes can become an effective instrument of security examination likely.Terahertz has many unique advantages in the field of security examination. First, with the pulse width of picosecond and femtosecond, THz radiation can be used to measure the time-domain spectroscope and transient characteristic of every material(including liquid, semiconductor, superconductor, specimen of biology). Second, terahertz photon only have few electron millivolt, compare with X-ray, terahertz can't destroy specimen for ionization. Third, terahertz radiation has strong penetrability to dielectric and wrapper such as plastic and wrapping paper.In this paper, THz Time-Domain Spectroscope is used to study the possibility of terahertz using in security examination. The following is a brief summary of the works conducted in this thesis and the experimental results achieved.The terahertz spectrums of ten sorts of limbers have been studied experimentally. The results show that the terahertz radiation can pass through these materials.We reported the experimental research to paper wrappers using terahertz technology, and discuss the transmission of terahertz radiation to wrappers through analyzing absorption coefficient and refractive index of these materials. The results show that the terahertz radiation can pass through these materials.