拓樸絕緣體薄膜Bi2Se2.1Te0.9飽和吸收的超快動力學應用

Abstract

拓樸絕緣體(topological insulators)因其特殊的物理性質，量子霍爾效應，而在近年來成為一種非常新穎的材料。本論文使用激發-探測方法去研究拓樸絕緣體硒碲化鉍(Bi2Se2.1Te0.9)薄膜的超快動力學，使用客製化鍍上拓樸絕緣體薄膜的鏡面，讓鈦藍寶石雷射經由拓樸絕緣體薄膜的飽和吸收性質而產生被動鎖模態。 研究結果使得拓樸絕緣體薄膜中的電子在飛秒(10-15 second)等級尺度下的超快動力學更加清晰，且拓樸絕緣體薄膜的非線性吸收可以使用z-scan方法觀察到。而在鈦藍寶石的雷射共振腔裡面，可以從有無裝置飽合吸收體的狀況下，從鎖模態中判斷其特性。

Topological insulator (TI) is a novel material because of its special physical property, Quantum Hall Effect. This thesis uses pump-probe method to study the ultrafast dynamics of the TI thin film of Bi2Se2.1Te0.9. Custom-made mirror coated with the TI thin film was used to passively mode-lock Ti:sapphire laser by saturable absorption in the TI film. The result has clarified ultrafast electronic dynamics of the TI thin film in femtosecond time region. The non-linear absorption of the TI thin film was studied by z-scan method. The Ti:sapphire laser cavity was constructed without and with installing saturable absorber to estimate its character under mode-locked condition.