建造準相位匹配高階諧波產生的拍波脈衝串; Construction of a Beat?Wave Pulse Train for Quasi?Phase?Matched High?Harmonic Generation

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题名:	建造準相位匹配高階諧波產生的拍波脈衝串;Construction of a Beat?Wave Pulse Train for Quasi?Phase?Matched High?Harmonic Generation
作者:	高仕麒;Kao,Shih-Chi
贡献者:	物理學系
关键词:	同調;軟 X 射線激光;高階諧波;雙色激光系統;脈衝串;soft x-ray laser;high-harmonic generation;two-color laser amplifier system;pulse train
日期:	2013-07-22
上传时间:	2013-08-22 11:47:10 (UTC+8)
出版者:	國立中央大學
摘要:	對於產生同調軟 X 射線激光在水窗區域,我們計劃聚焦主要激光在高原子數離子的介質,產生高階諧波。高階諧波產生的效率被主要激光和高階諧波的相位不批配限制。在反相位的高階諧波區域的電場和正相位的高階諧波的區域的電場會相消干涉,使高階諧波產生的效率強度不能建設性增加。然而,強度相對較弱的(1/100)反方向對撞激光可以破壞高階諧波產生在反相位的範圍。因此,我們建立雙色的激光放大系統,構建一個可控脈衝間隔時間的拍波脈衝序列,以對應準相位匹配條件使高階諧波可以建設性增加產生。雙色激光放大系統是 100-TW 激光系統的分支。它的中心波長為 800 nm。首先,它被是聚焦於充滿氪氣的長管中產生超連續光譜的產生。由於自相位調製,它可擴展頻譜到 900 nm。在那之後,我們送它進聲光調變器過濾為兩個尖峰的光譜。隨後,它進入到脈衝延展器的時間把時間延展從 50 fs 到 50 ps。最後,它通過第一級放大器和第二級放大器來放大能量。在脈衝壓縮器中,我們可以壓縮成短的脈衝時間和調整屋頂鏡延遲線在脈衝壓縮器中, 使雙色波的時間重疊間並形成拍波序列脈衝串。在那之後,我們要實驗這雙色激光系統可以構建我們想要的脈衝串。在這裡,我們用 20-TW 激光作為探針波與拍波在 BBO 上交叉產生和頻(SFG)。我們可以調整探測波延遲線來做互相關實驗。最後,在 600 fs 的脈衝串可以觀察到近 10 個清晰的脈衝。該脈衝間隔時間恰好對應高階諧波準相位匹配條件。 For generating coherent soft x-ray laser in the water window region, we plan to focus driving laser on the high-Z ions as interacting medium to generate high- harmonic generation. The efficiency of high-harmonic generation is limited by the phase-mismatch of driving laser and high-harmonic generation. The out-of phase high-harmonic generation field and in phase high-harmonic generation field cause destructive interference so that the efficiency of high-harmonic generation intensity can not constructively increase. However, a relatively weak intensity (1/100) counter-propagating laser can disrupt the high-harmonic generation emission from the out-of phase range. Therefore, we build the two-color laser amplifier system to construct a beat-wave pulse train with controllable pulse separation time to fit quasi-phase-matching condition of high- harmonic generation. The seed laser of the two-color laser amplifier system is from the 100-TW laser system branch. The center wavelength is 800 nm. First, it is focused on a long tube full of Kr gas to generate supercontinuum generation. The spectrum can be extended to 900 nm due to self-phase modulation. After that, we send it into Dazzler to filter the spectrum into two peaks. Then, it goes to stretcher to stretch the duration from 50 fs to 50 ps. After all, it gains energy through first-stage amplifier & second- stage amplifier. In the compressor, we can compensate the dispersion of chirp pulse to compress it into short pulse duration and adjust roof mirror delay line in the compressor to make two color waves temporal overlap and form beat-wave pulse train. After that, we want to examine that this two-color laser system can construct the pulse train we want. Here, we use 20-TW beam line as a probe wave to cross with beat-wave on BBO crystal generating sum-frequency generation (SFG). We can adjust the delay line of probe wave to do the cross-correlation experiment. Finally, these are nearly 10 clear pulses being obtained in a 600-fs pulse train. The separation time of pulses just fit quasi-phase-matching condition of high-harmonic generation.
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