克爾透鏡鎖模鈦藍寶石雷射之架設及其特性

Abstract

克爾透鏡鎖模鈦藍寶石雷射是近來研究超短脈衝光學的重要工具.它具有 可以產生十飛秒脈衝的潛力,而其共振腔相較以其他方式鎖模的雷射而言, 是更為單純的,不需外加複雜的元件,僅依靠本身的全光學調制即可達成鎖 模.在本論文中,我們提出一套理論計算的方法來進行共振腔設計.首先,以 對稱線型共振腔估計出曲面反射鏡的像散補償角.接著,便可根據對稱腔的 預估找出非對稱腔下的穩定區域並計算出晶體內的場分佈來找出可以產生 虛光闌效應的穩定區域的位置.最後,再計算激發透鏡所需的像散補償角. 實驗上,架設共振腔的詳細步驟亦於本論文中做了完整的記錄 .我們找出 了一套可以在短時間內從連續波輸出調成鎖模狀態的程序.此外,我們曾經 觀測到這個鎖模雷射自起動的現像,這將是未來重要的研究方向. Recently,kerr lens-mode locked Ti:Sapphire laser becomes an im- portant tool in the research of ultrafast optics.It has the pote- ntial to generate light pulses with pulse width down to 10 fs.Be- sides, its cavity is simple compared to other mode locked lasers, because its mode locking process relies on the all optical modul- ation generated by itself other than inserting extra complex com- ponents. In this thesis, we report a simple theoretical calculation met- hod which is provided for our cavity design. First, we use symme- trical linear cavity to estimate the astigmatism compensation an- gle of the curved mirrors. After then,we can find out exactly wh- ere the stable ranges locate in asymmetrical cavity according to the prediction from symmetrical case and calculate the field dis- tribution inside the crystal to see in which region the soft ape- rturing could be reached. Finally,the astigmatism- compensation gle that the pump lens needs to be rotated can be calculated. Also, the alignment and construction procedures during cavitytup are recorded detailly. A simple procedure to get KLM inort time is described. What comes more noticeably is that we had once observed the self-starting of this laser. It will be the major interest of our future research.