THz Time Domain Spectroscopy Based On Optical Rectification And Electro-optical Sampling By ZnTe

The radiation range from 0.1THz to 10 THz is called THz wave. A large number of sub-bands and micro-strip semiconductor energy lie in THz range. There are many biological macromolecules with resonance and rotational transition frequency distributed in THz band. Therefore, THz radiation has a unique spectral resolution.As a new detection technology, THz time domain spectroscopy based on THz radiation has an excellent performance in material resolution because of small photon energy and little structural damage of material. As a result, it has vast applications in the field of biomedicine, safety inspection and identification of cultural relics. This paper is mainly about the study of THz time-domain spectroscopy based on optical rectification and optical sampling by Zn Te crystal. The main contents of the article are as follows.In chapter one, I give an overview of the background and research at home and abroad. At first, a brief description of position and reason of "THz gap" is shown. Then I briefly give an introduction of the unique properties and applications of THz wave as well as the domestic and foreign research of THz radiation.In chapter two, I mainly introduce the methods to generating THz wave and the sources of THz wave. According to the excitation mode, the generating methods involved will be divided into two major categories of optics and electronics.In chapter three, I will illustrate the principle of THz time-domain spectroscopy system. At first, the far-field form of the electric field of the pulse radiated from the polarization induced by optical field is derived from the Maxwell equations. Then I give the form of electromagnetic pulse radiation field generated from the Zn Te crystal based on optical rectification. Then carry out the thorough analysis to the electro-optic effect in a nonlinear crystal which is used in optical sampling detection by Zn Te crystal.In chapter four, I mainly analyze the experimental results. Firstly, I give a brief illumination of the THz time-domain spectroscopy system we set up. Then I using the system to study the absorption of water vapor in the THz band. Next, measuring the transmission of the silicon wafer and silicon substrate plated with ITO nanofilm in THz spectrum, the results coincide with the simulation very well. At last, I give the simulation of the extraordinary properties of nanofilms with silicon substrate in unique angle.