InGaAlAs/AlGaAs飽和布拉格反射鏡產生之非線性飽和吸收與反射率之研究

Abstract

本文中主要探討的是由布拉格反射鏡所產生的非線性 光吸收與反射．一般而言，此元件 結構可視為在高反射 率布拉格鏡的頂層成長能提供非線性飽和吸收的InGaAlAs/AlGaAs 多重 量子井．此量子井的光吸收特性控制了主要的被動鎖模機制．整個元件的 結構是用分子束磊 晶的方法所成長，我們成功地利用它來 被動鎖模Ti:sapphire雷射以得到100飛秒的短脈衝輸 出 ．我們嘗識藉著改變不同的磊晶厚度來觀察反射率的變化，並且經由模擬 的結果來做比較 ．實驗結果顯示：當量子井的吸收波長 能夠位於布拉格反射鏡的高反射率波帶時，被動鎖模 得到的脈衝特性都能獲得改善．此外，本文也將針對應變量子井的光學特 性及被動鎖模的動 力理論提出討論． In this thesis, we studied the nonlinear saturable absorption and reflectivity of the saturable Bragg reflectors. The device structure can be regarded as a high reflectivity Bragg mirror incorporated with semiconductor InGaAlAs/AlGaAs muilti- quantum wells. These wells are used as saturable absorbers whose optical property dominates the dynamics of passive mode-locking. The overall device structure is controlled by molecular beam epitaxy (MBE) . It is successfully used for passive mode locking the Ti:sapphire laser to obtain 100fs ultra-short pulses. Besides,we observe the alteration of reflectivity by changing the thickness of epitaxial lay ers and compare it with simulation results. the experimental data shows that when the absorption peak of the multiquantum wells is located within the high-broad re -flection band, the charateristics of the output pulses, such as pulse width, tun -ing range, and stability...etc.,can be highly improved. Finally, the optical pro -perties of strained quantum well and the dynamics of mode-locking are also diss- cussed.