Electro-optic Sampling To The Material Properties Of Thz Spectroscopy To Detect The Impact

Idealy, the THz pulse shape is that measured directly, but the THz pulse shape obtained is distorted in experiment. This distortion is caused by several factors, one is the phase matching of the electro-optic sampling process, another one is the dispersive and reflection in the process of THz pulse propagation in the which crystal the THz pulses are generated and the electro-optic sampling crystal. The absorption of ambient water vapor can also lead to distortion.This thesis studies the character of the electro-optic crystal which affects the THz pulse detection. The properties of these electro-optic crystal include: transverse-optical- (TO) phonon resonance frequency dielectric constant, refractive index, absorption coefficient, etc. the character of these electro-optic crystal limit abilitivity of detection. We used the ZnTe crystal, in which the transverse optical phonon frequency at 5.3 THz, This makes around the THz pulse frequency of 5.3 THz is absorbed by the resonance, So its detection frequency range of 0-5 THz. In foreign countries, instead of using GaP crystal by ZnTe crystals, the frequency range extended to 0-7 THz.According to the relevant physics formulas .We make a program by Matlab, to simulate the changes of the crystal THz pulse detection property. The research is contributed to the in THz pulse reconstruction and detection crystal choice. In addition, the ultrafast-femtosecond Dynamics of THz contribute to a deeper for understanding of the process. The carrier life related with THz pulse width of the spectrum, by the carrier lifetime measurements can be found out THz pulse properties of THz pulse width of the spectrum. This thesis has already some results: (1)In accordance with the relevant formula using Matlab simulation procedures the THz pulse propagation in the medium, THz pulse dispersion in the medium, THz pulse reflection of the crystal surface as well as the pulse phase matching, which will influence the THz pulse. These effects have already been in the experiment performance, we will now rise to the theory, And get some results, these results include: THz pulse in the medium dispersion characteristics will lead to THz pulse of high-frequency part absorption, crystal surface reflection will lead to high frequency components easily reflection, the detection phase-matched will affect the THz pulse waveform. (2)We simulate in the different detection crystal for the high-frequency THz pulse characteristics. We found the transverse phonon resonance is an important parameter affected the detection properties .THz pulse frequency distribution around the transverse phonon resonance frequency will vanish due to the resonance absorption, Detection THz spectrum will be deficiencies. We found that by using of the higher of transverse phonon frequency in crystal, such as GaP crystal, and so on, the better of high-frequency THz pulse detection performance.(3) The physical mechanism of the THz pulse femtosecond pulses of ultrafast excitation process is studied. We have measurement carrier lifetime of semi-insulating GaAs. By measurement of the pump pulse and probe pulse intensity and the intensity of 10:1, measured results would be better.In summary, the influence the various factors to THz pulse detection, Through simulation and theory analysis we found the crystal transverse phonon resonance frequency crystal is an important parameter which impact detection properties, the higher of transverse phonon resonance frequency in crystal, such as GaP crystal, and so on, the better of high-frequency THz pulse detection performance.