| Terahertz radiation refers to the narrow electromagnetic wave band which covers fromthe microwave to the infrared wave band. Since1980’s, great progress has been made inultra-fast laser technology and femtosecond pulse laser has become the steadiest excitationoptical source for the THz pulses generation, which greatly drives the development andapplication of the whole THz science and technology. THz time-domain spectroscopy, a newand promising coherent technique, is popularized and widely used due to its high timeresolution in picosecond’s range, high signal to noise ratio and no dependence onKramers-Kronig relation to obtain refraction index information. So THz-TDS has beenstudied and utilized more and more these years.Utilizing the facilities provided by the research center of THz, Wuhan NationalLaboratory for Optoelectronics in HUST, this paper investigated many medicines and severalsamples of the asphalt with different wax content and made an analysis of their frequency,absorption and transmittance spectrum. Since the energy gap of much material’s molecularvibration is located in THz range, a detection and identification of materials can be made byfinding out their different effective frequency range and characteristic absorption peaks. TheTHz spectrums of medicines given in chapter3enrich our fingerprint spectra database.In chapter4, considering the recent research still remaining on distillation andadsorption method, we make a bold attempt to study petroleum and asphalt in THztime-domain spectroscopy. An analysis is qualitatively made of the relation between wave’speak decay, phase delay and asphalt’s wax content, and according to this, we can decidewhether the asphalt is qualified. Last, a more strict idea is developed that we had better mixthe wax separated by distillation back to the asphalt for a better sample. The research of thispaper shows that THz time-domain spectroscopy has great use and potential in identificationand quality detection. |
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