光混頻產生之連續波兆赫輻射同調性之研究

Abstract

我們架設了一套輕便(系統大小為50X50cm2)、便宜且輸出波長可調的連續波光源系統，來產生兆赫輻射。為了配合偵測器，我們使用Martin-Puplett 干涉儀來量測。 本論文主要利用不同載子生命期的光導天線(半絕綠砷化鎵及低溫成長砷化鎵)來產生連續波兆赫輻射，並量測其同調長度、分析。經過我們的實驗及計算推論，來得到光導天線之載子生命期和所輻射之連續波兆赫輻射的同調長度間的關連性，進而來最佳化我們連續波兆赫輻射的出輸。跟據計算，CW THz 的線寬約為84.68MHz，而相對的同調長度為350公分以上，而實驗所量測同調長度為120公分以上，相對的線寬約為300MHz。對於此差異，我們給予合理的解釋。

We establish a small, inexpensive and movable CW THz light source to generate CW THz. In order to detect the CW THz radiation, we use Martin-Puplett interferometer with bolometer to measure it. In this thesis, we mainly use photoconductive antennas with different carrier lifetime (Semi-Insulating GaAs and Low-Temperature grown GaAs) to generate CW THz field, measure and analysis the difference of coherence length. According to our experiment and calculation, we want to find the relation between the carrier lifetime of the photoconductive antenna and the coherence length of the emitted CW THz radiation. According to our calculation , the linewidth of the CW THz radiation was about 84.68MHz, the corresponding coherence length was above 350cm. Compare with our measured coherence length of above 120cm, the corresponding linewidth was about 300MHz. we will give the reasonable answer about the difference between calculation and experiment.