以外部電光取樣方法探測在砷化鎵上產生的數微微秒級電脈衝信號之研究

Abstract

本實驗目標:製作光導開關並使用藍寶石雷射作為光源的外部電光取樣系 統,以之測試光導開關的響應.我們利用半絕緣性砷化鎵與質子轟擊式砷化 鎵兩種不同材料來研製光導開關,以Lithium tantalate為電光晶體,並以 光波長0.8micron的被動鎖模摻鈦藍寶石雷射為光源,架設一套外部電光取 樣系統,來對光導開關之時域響應進行非侵害,非接觸式測量.以半絕緣性 砷化鎵光導和質子轟擊式砷化鎵光導量測為例,以被動鎖模摻鈦藍寶石雷 射約250femtosecond的光脈衝激勵下,半絕緣性砷化鎵光導可產生56 picrosecond寬的電脈衝,以及3.5picrosecond的上升時間;而質子轟擊式 砷化鎵光導可產生2.5picrosecond寬的電脈衝,以及1.4picrosecond的上 升時間.因此可證實本系統之時間解析度在1.4~3.5picrosecond之間. We have studied the characteristic of photoconductive switch fabricated on Semi-insulating and proton-bombarded GaAs substrates. respectively, Using 0.8 micron passive-mode-locked Ti:Sapphire laser, the temporal resopone of these devices have been measured via an external electro-optic sampling system. Under the illumination of 250 femtosecond optical pulse-train, the S.I. GaAs photoconductive switch can generate a 56 picrosecond electrical pulse with it's rise time of about 3.5 picrosecond. To date, a ultrashot electrical pulse with it's FWHM and rise time of about 2.5 picrosecond and 1.4 picrosecond has been observed on the proton-bombarded GaAs photoconductive switch, respectively, The temporal resolution has been estimated to be 1.4~3.5 picrosecond.