本文選題：光纖激光器 + 頻域動力學(xué)　； 參考：《國防科學(xué)技術(shù)大學(xué)》2015年博士論文

【摘要】：論文針對光纖環(huán)形激光器(FRL)在工程應(yīng)用中出現(xiàn)的復(fù)雜多模動態(tài)現(xiàn)象,通過改進多通道實時頻域觀測手段,突破傳統(tǒng)激光動力學(xué)測量技術(shù)的頻域限制,將人們對FRL非線性動力學(xué)特性的認識從低維拓展至高維,揭示了模式個體行為與集群行為之間的復(fù)雜關(guān)聯(lián)及內(nèi)在物理機制。激光頻域動力學(xué)問題是光學(xué)復(fù)雜系統(tǒng)研究領(lǐng)域的一大難題。FRL是典型的大自由度光學(xué)復(fù)雜系統(tǒng),具有復(fù)雜跳模、高維混沌等非線性模式動態(tài)行為。現(xiàn)有的理論模型及測量手段大多只關(guān)注密集模式群落的整體行為,而忽視了模式個體行為;這一降維處理方式丟失了大量的頻域模式動態(tài)信息,導(dǎo)致跳模抑制、高維頻域混沌產(chǎn)生及控制等頻域非線性動力學(xué)問題無法得到有效處理。要解決這些問題,需在理論上建立包含密集縱模間相互作用與耦合機制的物理模型,更需發(fā)展多模激光模式動態(tài)行為測量的實驗手段。論文以摻鉺光纖環(huán)形激光器(EDFRL)作為研究對象,通過引入密集縱模間的交叉耦合系數(shù),并考慮鉺離子對猝滅效應(yīng)而引入額外自由度,建立了雙模及多模光纖激光頻域動力學(xué)模型,可有效描述頻域內(nèi)大量模式的個體行為及集群行為,在理論上重現(xiàn)了頻域高維動力系統(tǒng)所特有的多模動態(tài)特性。仿真結(jié)果表明,通過改變離子對濃度或抽運系數(shù),所有模式可通過陣發(fā)、倍周期分岔、準周期等途徑同步進入混沌,關(guān)聯(lián)維數(shù)高達5.1。為實驗獲取光纖激光多模動態(tài)信息,提出一種基于光學(xué)外差和時頻分析技術(shù)(OH-JTFA)的頻域動態(tài)測量方法,實現(xiàn)了EDFRL密集模式頻率及強度多參量時間序列的同步提取,頻率分辨率在kHz量級。分別考察了單FBG選模EDFRL、自組織反饋EDFRL、調(diào)制型混沌EDFRL等三類光纖激光系統(tǒng)的頻域動態(tài)特性,以揭示模式個體行為與群體行為間的復(fù)雜互動及演化規(guī)律。單FBG選模EDFRL常被認為是最典型的單波長激光系統(tǒng),實際上在選模通道內(nèi)寄居上百個本征模式,自由運轉(zhuǎn)條件下輸出非穩(wěn)態(tài)多縱模(MLM)。通過采用OH-JTFA方法,首次清晰測得該類EDFRL輸出密集多模呈現(xiàn)的豐富局域動態(tài)現(xiàn)象,發(fā)現(xiàn)模式群落整體行為處于光強穩(wěn)態(tài)時,模式個體行為可呈現(xiàn)典型的混沌特征。自組織反饋EDFRL在腔內(nèi)引入飽和吸收體形成超窄帶自適應(yīng)光柵,理論上可始終保持單縱模(SLM)穩(wěn)定輸出。然而,真實激光器存在多類型的跳�，F(xiàn)象,受限于常規(guī)跳模檢測手段,而無法有效獲取跳模全過程的關(guān)鍵信息。通過采用OH-JTFA方法,實現(xiàn)了對跳模全動態(tài)過程的實時監(jiān)測,跳模過程由時頻瀑布圖直觀呈現(xiàn),首次無失真地獲取到跳模瞬態(tài)過程的所有物理參量。調(diào)制型混沌EDFRL通過引入一個自由度,使總光強呈混沌輸出,是典型的低維混沌系統(tǒng)。同樣,該系統(tǒng)輸出光場包含大量密集縱模,當總光強輸出為混沌態(tài)時頻域內(nèi)各模式動態(tài)特性及演化規(guī)律迄今仍不清楚。通過提高OH-JTFA的頻域分辨率,同步提取出單個模式頻率、譜線及光強等多參量時間演化特性;發(fā)現(xiàn)當總光強為低維混沌輸出時,單個模式在頻域上出現(xiàn)頻率調(diào)制及譜線加寬現(xiàn)象、在強度上呈現(xiàn)高維混沌或隨機特征。論文中得到的重要實驗結(jié)果及創(chuàng)新點主要包括以下三個方面:1、通過OH-JTFA方法在單FBG MLM-EDFRL中發(fā)現(xiàn)了一類大自由度非線性動力系統(tǒng)所特有的動態(tài)現(xiàn)象。測量結(jié)果表明,局域模式產(chǎn)生了總光強所無法呈現(xiàn)的頻域動態(tài)行為,包括模式自脈沖、模式反相動態(tài)、混沌多模振蕩、隨機多模振蕩等。2、利用OH-JTFA方法首次獲得了自組織反饋SLM-EDFRL典型跳模及瞬時多模振蕩演化過程的時頻瀑布圖。本方法是迄今唯一能實現(xiàn)同步提取EDFRL跳模持續(xù)時間、跳模間距與方向、參與競爭的模式數(shù)量、模式強度演化等跳模參數(shù)的頻域測量手段,為深入理解模式失穩(wěn)及動態(tài)機理提供了更全面的觀測手段,具有重要的參考價值。3、通過提高OH-JTFA的頻域分辨率,考察了抽運調(diào)制型混沌光纖激光系統(tǒng)的頻域動力學(xué)特性,發(fā)現(xiàn)了總光強表現(xiàn)為典型的低維混沌時,頻域內(nèi)存在的大量縱模表現(xiàn)出極為復(fù)雜的高維動態(tài)特性。對各模式進行的非線性時間序列分析表明具有混沌特性的模式與具有隨機演化特性的模式在總的低維混沌下共存。在此基礎(chǔ)上,進一步探討了利用混沌光纖激光器頻域內(nèi)的大量混沌/隨機模式作為光子熵源來生成多通道物理隨機碼的可行性。
[Abstract]:In this paper, the complex multimode dynamic phenomenon of fiber ring laser (FRL) is used in the engineering application. By improving the multi-channel real-time frequency domain observation method, the frequency domain limitation of the traditional laser dynamic measurement technology is broken through. The understanding of the nonlinear dynamic characteristics of the FRL is extended from low dimension to high dimension, and the individual behavior and set of the model is revealed. The complex association and internal physical mechanism between group behavior. The problem of laser frequency domain dynamics is a major problem in the field of optical complex systems..FRL is a typical large degree of freedom optical complex system with complex dynamic behavior such as complex mode jumping, high dimensional chaos and so on. Most of the existing theoretical models and measurement means are mostly focused on the intensive mode. The whole behavior of the community is ignored, and the pattern individual behavior is ignored. This way of reducing the dimensional dynamic information in frequency domain, which leads to the suppression of die hopping, and the nonlinear dynamic problems in frequency domain, such as high dimensional frequency domain chaos generation and control, can not be effectively dealt with. The physical model of interaction and coupling mechanism needs to develop the experimental means of dynamic behavior measurement in multimode laser mode. The paper uses an erbium doped fiber ring laser (EDFRL) as the research object. By introducing the cross coupling coefficient between the dense longitudinal modes and introducing the additional degree of freedom for the quenching effect of Erbium ion, the two mode and multi modes are established. The frequency domain dynamic model of the optical fiber laser can effectively describe the individual behavior and cluster behavior of a large number of modes in the frequency domain. In theory, the multimode dynamic characteristics peculiar to the high dimensional power system in the frequency domain are reproduced. The simulation results show that by changing the ion pair concentration or pumping coefficient, all patterns can pass through the formation, the period doubling bifurcation, the quasi periodic and so on. The path synchronization enters chaos, and the correlation dimension is up to 5.1. to obtain the multi mode dynamic information of optical fiber laser. A frequency domain dynamic measurement method based on optical heterodyne and time-frequency analysis technology (OH-JTFA) is proposed. The synchronous extraction of multi parameter time series of frequency and intensity in EDFRL intensive mode is realized. The frequency resolution is in the order of kHz. Single FBG mode selection EDFRL, self organizing feedback EDFRL, modulated chaotic EDFRL and other three kinds of optical fiber laser systems are dynamic in frequency domain to reveal the complex interaction and evolution law between mode individual behavior and group behavior. The single FBG mode selection EDFRL is often considered as the most typical single wavelength laser system, and in fact resides hundreds of eigenvalues in the mode selection channel. In the mode, the unsteady multi longitudinal mode (MLM) is output under free running condition. By using the OH-JTFA method, the rich local dynamic phenomenon of the EDFRL output dense multimode is clearly detected for the first time. It is found that the pattern community's behavior can show the typical chaotic characteristics when the whole behavior of the pattern community is in the light steady state. The self organizing feedback EDFRL is introduced in the cavity. The saturated absorber forms a super narrow band adaptive grating, which can always maintain the stable output of the single longitudinal mode (SLM) in theory. However, there are many types of die jumping phenomenon in the real laser, which is limited by the conventional mode hopping method, but can not effectively obtain the key information of the whole process of the die hopping. Through the OH-JTFA method, the full dynamic process of the die hopping is realized. In real time monitoring, the hopping process is presented directly by the time frequency waterfall graph, and all physical parameters of the transient process are obtained without distortion for the first time. The modulated chaotic EDFRL is a typical low dimensional chaotic system by introducing a degree of freedom to make the total light intensity chaotic output, and the output light field of the system contains a large number of dense longitudinal modes, when the total intensity of light is strong. The dynamic characteristics and evolution laws of each mode in the frequency domain are still unclear. By improving the resolution of the frequency domain of OH-JTFA, the time evolution characteristics of multiple parameters, such as single mode frequency, spectral line and light intensity, are extracted synchronously. It is found that when the total light intensity is low dimensional chaotic output, the frequency modulation and spectral lines appear in the frequency domain by a single mode. The important experimental results and innovation points in this paper mainly include the following three aspects: 1, the dynamic phenomena of a class of large degree of freedom nonlinear dynamical systems are found in a single FBG MLM-EDFRL by OH-JTFA method. The results show that the local mode produces the total. The frequency domain dynamic behavior that the light intensity can not present, including the mode self pulse, the pattern inverse phase dynamics, the chaotic multimode oscillation, the random multimode oscillation, and so on, uses the OH-JTFA method to obtain the time frequency waterfall diagram of the self organized feedback SLM-EDFRL typical model and the transient multimode oscillation evolution process for the first time. This method is the only method to achieve the synchronous extraction of EDFRL in SLM-EDFRL. The duration of die jumping, the distance and direction of the die, the number of modes involved in the competition and the frequency domain measurement of the model strength evolution, provide a more comprehensive observation method for understanding the mode instability and dynamic mechanism, which has important reference value.3. By improving the resolution of OH-JTFA in frequency domain, the pump modulation chaos is investigated. In the frequency domain dynamics of the optical fiber laser system, it is found that when the total light intensity is characterized by a typical low dimensional chaos, a large number of longitudinal modes in the frequency domain show very complex high dimensional dynamic characteristics. The nonlinear time series analysis of the modes shows that the mode with the chaotic characteristic and the pattern with random evolution characteristics are generally low. On this basis, the feasibility of using a large number of chaotic / random modes in the frequency domain of a chaotic fiber laser as a photon entropy source to generate multi-channel physical random codes is further discussed.
【學(xué)位授予單位】：國防科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TN248

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