利用飛秒脈衝雷射激發釔鋇銅氧高溫超導薄膜產生泰拉赫茲輻射之研究

Abstract

本論文是研究利用飛秒脈衝雷射激發釔鋇銅氧高溫超導薄膜，產生泰拉赫茲輻射(Terahertz, THz radiation)，並利用自由空間電光取樣系統來量測THz電磁輻射的時域暫態波形，這是首次利用電光取樣方式量測高溫超導(HTSC)元件的THz電磁輻射。將波形作傅力葉轉換，得知其頻譜範圍由0.1 THz延伸至4 THz以上，而最大值出現在0.6 THz。我們研究THz電磁輻射的訊號強度隨薄膜溫度，偏壓電流以及激發光的功率的變化情形，並以飛秒雷射光致超導電流之遽變來解釋高溫超導元件產生THz輻射的原因

In this thesis, emission of terahertz (THz) electromagnetic radiation pulses from current-biased high-Tc superconductivity (HTSC) YBCO thin films has been studied by excited with femtosecond laser pulse. The electric field of the THz radiation was measured by a free-space electro-optic sampling (FSEOS) technique. It is the first time to measure the THz radiation from HTSC by FSEOS. The Fourier transform of the waveform of the pulses reveals that the amplitude spectrum extended from 0.1 THz to 4 THz with its peak at 0.6 THz. The sample temperature, bias current, and pump power dependence of the THz radiation has been investigated. The radiation is explained in terms of the ultrafast supercurrent modulation caused by the fs laser pulse.