拓樸絕緣體產生兆赫波輻射機制之研究

Abstract

本論文利用兆赫波時析頻譜研究拓樸絕緣體碲化鉍晶體所產生的兆赫波輻射特性。由實驗結果顯示，兆赫波電場強度和樣品的載子濃度有很密切的關連性。此外，也發現以近紅外(800 nm)光脈衝進行激發，無論從正向(basal plane, ab-plane) 的晶面進行光激發或從側向(edge plane, ac- or bc-plane)的晶面進行光激發，皆可產生兆赫波輻射，且由側向的晶面所產生的兆赫波電場強度是由正向晶面所產生的兆赫波強度的四十倍以上。最後，本論文亦針對拓樸絕緣體產生兆赫波的機制進行討論，並分析其與拓樸絕緣體狄拉克表面態之間的關係。

In this thesis, we study the characteristics of terahertz (THz) radiation generated from the topological insulator Bi2Te3 by Terahertz-Time Domain Spectroscopy in our group. The THz output power is strongly dependent on the carrier concentrations. Additionally, the THz wave can be generated from both the basal plane (ab-plane) and the edge plane (ac- or bc-plane) of topological insulator single crystals by 800-nm pulse pumping. The THz wave generated from the edge plane is over forty times higher than that generated from the basal plane. The THz generation mechanism on topological insulators and even the correlation between THz wave generation and the Dirac surface state of topological insulators will be discussed.