Comparison studies between the THz-TDS method and the spectral encoding method

Abstract

THz waves have diverse applications in science and technology. One of the applications is plasma diagnostics, especially for fusion plasmas. So far the THz time-domain spectroscopy (THz-TDS) method has been used for plasma diagnostics before, but the THz-TDS method takes a long time for plasma diagnostics as scanning in time requires a little long time. Hence, the THz-TDS method is not a good way to measure the plasma density which fluctuates in a short time scale. In this sense, the development of a better diagnostic method is required. In this thesis, we developed a new way for THz diagnostics that can be used for plasmas, where the THz waveform can be measured by the spectral encoding method. Of course, the two methods may be slightly different and we investigated those issues in detail. The research results show that ZnTe crystals with different thicknesses have the velocity mismatching effect and thicker crystals have longer pulse durations. Eventually, this result may be used for accurate measurement of plasma densities