本文關(guān)鍵詞： 飛秒激光 頻率分辨 相位級(jí)聯(lián) 矩形濾波 高斯濾波　出處：《華中科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：從20世紀(jì)60年代梅曼發(fā)明紅寶石激光器開始,人們一直致力于激光技術(shù)的改進(jìn),從連續(xù)激光到調(diào)Q激光再到基于鎖模技術(shù)的皮秒、飛秒激光[1],激光的脈沖寬度變得越來越窄,峰值功率越來越高,其在科學(xué)實(shí)驗(yàn)及生產(chǎn)中的應(yīng)用也變得越來越廣.作為一個(gè)基礎(chǔ)性的工作,對(duì)于激光脈沖尤其是皮秒、飛秒激光,如何測(cè)量其脈沖寬度及相位成為激光應(yīng)用首先要解決的問題。對(duì)于納紗量級(jí)的激光脈沖,僅用示波器就可以測(cè)定其脈沖的寬度,而對(duì)于皮秒或飛秒量級(jí)的脈沖,電子的示波器由于響應(yīng)速度不夠快,無法測(cè)量其脈沖寬度,條紋相機(jī)或是改進(jìn)的條紋相機(jī)雖然可以測(cè)量其脈寬,但是條紋相機(jī)本身的價(jià)格十分昂貴,無法普及.事實(shí)上,科學(xué)家先后提出三種更為常見的超短脈沖脈寬及相位測(cè)量方法:自相關(guān)法(AC)、頻率分辨光學(xué)開關(guān)法(FROG)、基于譜相干的脈沖電場(chǎng)重構(gòu)法(SPIDER).本文所采用的方法是基于譜相干的脈沖電場(chǎng)重構(gòu)法.利用頻率上具有一定側(cè)切量的兩束脈沖進(jìn)行干涉,對(duì)干涉譜中所包含的相位信息通過傅里葉變換及相位積分或級(jí)聯(lián)的方法對(duì)相位進(jìn)行重構(gòu),在此基礎(chǔ)上,再結(jié)合原始脈沖頻譜對(duì)脈沖在脈沖的脈寬進(jìn)行重構(gòu).本文主要的研究?jī)?nèi)容如下:研究了飛秒激光脈沖線性自相關(guān)、強(qiáng)度自相關(guān)及譜相干的聯(lián)系與區(qū)別,初步論證了譜相干技術(shù)應(yīng)用于飛秒激光脈沖脈寬及相位測(cè)量中的可行性,完整給出了相位級(jí)聯(lián)重構(gòu)法的原理及優(yōu)化方法.研究了側(cè)切量的引入對(duì)于譜相干干涉譜的影響,采用數(shù)值模擬的方式定量描述了側(cè)切量對(duì)于時(shí)域干涉信息分布的影響,針對(duì)時(shí)域干涉信息分布圖,給出了合理的矩形及高斯濾波函數(shù)選取方法.討論了BBO晶體不同類型的相位匹配對(duì)于側(cè)切干涉譜及非側(cè)切干涉譜匹配帶寬的影響,確定了BBO晶體匹配類型及厚度等參數(shù),針對(duì)實(shí)驗(yàn)對(duì)展寬脈沖脈寬的要求,計(jì)算并確定了光柵對(duì)的參數(shù).研究了二次脈寬及相位重構(gòu)的可行性,通過比對(duì)分析,得出關(guān)于二次脈寬及相位重構(gòu)法的一般性結(jié)論.討論了相位重構(gòu)過程中相位解纏繞與側(cè)切非側(cè)切干涉相位信息整合先后順序?qū)τ谙辔恢貥?gòu)的影響.數(shù)值模擬表明,相位解纏繞與側(cè)切非側(cè)切干涉譜相位信息整合先后順序?qū)τ谙辔坏闹貥?gòu)結(jié)果有較大的影響,而基于重構(gòu)的相對(duì)所得到的相位余弦隨頻率變化圖是一致的.提出了對(duì)SPIDER的改進(jìn)方案,對(duì)近十年來以減少測(cè)量誤差、提高測(cè)量效率為目的的實(shí)驗(yàn)方案進(jìn)行簡(jiǎn)單的介紹.本文基于自主搭建的SPIDER實(shí)驗(yàn)裝置,對(duì)本實(shí)驗(yàn)室中現(xiàn)有飛秒激光進(jìn)行脈沖寬度及相位的測(cè)量,通過光譜的采集及Labview程序處理,重構(gòu)了得到39的脈沖寬度及相對(duì)相位隨頻率變化曲線,所重構(gòu)的相對(duì)相位與實(shí)際相符,而脈寬則與實(shí)驗(yàn)室中自相儀所測(cè)量得到的37.38的實(shí)驗(yàn)結(jié)果符合得較好.
[Abstract]:Since the invention of ruby laser in 1960s, people have been devoted to the improvement of laser technology, from continuous laser to Q-switched laser to picosecond, femtosecond laser based on mode-locked technology. [1. The pulse width of laser becomes narrower and the peak power becomes higher and higher. As a basic work, laser pulse, especially picosecond, becomes more and more widely used in scientific experiments and production. Femtosecond laser, how to measure its pulse width and phase becomes the first problem to be solved in laser application. For nanosecond laser pulse, the pulse width can be measured only by oscilloscope. For picosecond or femtosecond pulse, the electronic oscilloscope can not measure the pulse width because the response speed is not fast enough. The fringe camera or the improved stripe camera can measure the pulse width. In fact, scientists have proposed three more common methods for measuring the pulse width and phase of ultrashort pulses: the autocorrelation method. Frequency resolved optical switch (FROG). Spectral coherence based pulsed electric field reconstruction method is used in this paper, which is based on spectral coherent pulse electric field reconstruction method. Two pulses with certain side tangent are used to interfere. The phase information contained in the interference spectrum is reconstructed by Fourier transform and phase integration or concatenation. The main contents of this paper are as follows: the relationship and difference of linear autocorrelation, intensity autocorrelation and spectral coherence of femtosecond laser pulses are studied. The feasibility of spectral coherence technique in pulse width and phase measurement of femtosecond laser pulses is preliminarily demonstrated. The principle and optimization method of phase concatenation reconstruction are presented, and the influence of side tangent on spectral coherent interference spectrum is studied. The influence of side tangent on time domain interference information distribution is quantitatively described by numerical simulation, aiming at the time domain interference information distribution map. A reasonable selection method of rectangular and Gao Si filtering functions is given, and the influence of different types of phase matching in BBO crystal on the bandwidth of side-cut interference spectrum and non-side-cut interference spectrum matching is discussed. The matching type and thickness of BBO crystal are determined. The parameters of grating pair are calculated and determined according to the requirement of broadening pulse width. The feasibility of secondary pulse width and phase reconstruction is studied. Through comparative analysis. The general conclusion about the method of quadratic pulse width and phase reconstruction is obtained, and the influence of the sequence of phase information integration of phase unwinding and non-side tangent interference on phase reconstruction is discussed. The numerical simulation shows that the phase reconstruction is affected by the sequence of phase unwinding and non-side tangent interference. . The sequence of phase information integration between phase unwinding and non-side tangent interference spectrum has great influence on the phase reconstruction results. The relative phase cosine based on the reconstruction is consistent with the frequency change diagram. An improved scheme for SPIDER is proposed to reduce the measurement error in the last ten years. Based on the self-built SPIDER experimental device, the pulse width and phase of femtosecond laser in our laboratory are measured. Through spectrum acquisition and Labview program processing, the pulse width and relative phase curves of 39 with frequency are reconstructed, and the reconstructed relative phase is in accordance with the actual situation. The pulse width is in good agreement with the experimental results of 37.38 measured by the self-phase analyzer in the laboratory.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN24

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