【摘要】：2 μm波段脈沖激光在醫(yī)療、國(guó)防、機(jī)械加工和光通信等領(lǐng)域都有很大的應(yīng)用前景。主動(dòng)鎖模光纖激光器利用的鎖模方式一般是引入外界信號(hào)使激光器腔體內(nèi)的參量達(dá)到周期性變化,但由于其調(diào)制器頻率的限制,導(dǎo)致輸出激光脈沖的重復(fù)頻率受限,無(wú)法實(shí)現(xiàn)高重復(fù)頻率的超短脈沖。有理數(shù)諧波鎖模技術(shù)是對(duì)基于調(diào)制器鎖模技術(shù)的改進(jìn)方案。本文研究有理數(shù)主動(dòng)鎖模技術(shù),建立了有理數(shù)主動(dòng)鎖模摻銩脈沖激光器的理論模型,通過(guò)理論仿真,分析組成鎖模激光器的各參數(shù)對(duì)激光器輸出脈沖特性的影響,期望在壓窄輸出激光脈沖寬度的基礎(chǔ)上,提高脈沖的重復(fù)頻率,從而解決調(diào)制頻率的限制問(wèn)題的方法,獲得基于有理數(shù)主動(dòng)鎖模的2 μm波段超短激光脈沖。本文的主要工作為:1,建立了有理數(shù)主動(dòng)鎖模摻銩脈沖光纖激光器的數(shù)值仿真模型,仿真模型由摻銩光纖放大器模型、普通單模光纖中脈沖傳輸模型和調(diào)制器模型這三部分組成。詳細(xì)分析了三個(gè)部分在2μ 波段有理數(shù)諧波脈沖激光的形成過(guò)程中的作用。2,分析了不同倍頻情況下,2 μm波段脈沖激光時(shí)域波形和頻域的穩(wěn)定性。仿真結(jié)果表明,通過(guò)較小的調(diào)制頻率即可輸出高重復(fù)頻率的鎖模脈沖。激光器在時(shí)域上輸出18倍頻脈沖所用到的調(diào)制頻率為fm= 3.6fc,即基頻的3.6倍。并且在頻域上分析激光器的穩(wěn)定性,結(jié)果表明:有理數(shù)主動(dòng)鎖模技術(shù)的穩(wěn)定性比普通主動(dòng)鎖模技術(shù)的穩(wěn)定性差,并且隨著階數(shù)的增加穩(wěn)定性隨之而降低。3,研究了有理數(shù)主動(dòng)鎖模摻銩光纖激光器輸出的超短脈沖功率、脈寬以及能量參數(shù)隨有源光纖的長(zhǎng)度、摻雜濃度、泵浦光功率及單模光纖的非線性等變化的特性。仿真結(jié)果表明,在一定的銩離子摻雜濃度范圍內(nèi),輸出功率隨摻雜濃度的增加而線性增加,脈寬則隨之變窄;在一定范圍內(nèi)增加摻銩光纖的長(zhǎng)度能夠提高激光器輸出脈沖功率并有效降低脈寬;普通單模光纖的非線性效應(yīng)主要影響輸出脈沖的脈寬,通過(guò)優(yōu)化光纖長(zhǎng)度可獲得最窄脈寬的脈沖激光輸出;在適當(dāng)范圍內(nèi)增加泵浦光功率和調(diào)制器的調(diào)制深度,均可提高輸出激光脈沖的功率并有利于壓窄脈寬。
[Abstract]:2 渭 m-band pulse laser has great application prospects in medical, national defense, mechanical processing and optical communication. Active mode-locked fiber lasers usually introduce external signals to make the parameters of the laser cavity change periodically. However, due to the limitation of the modulator frequency, the repetition rate of the output laser pulse is limited. Ultra-short pulses with high repetition rates cannot be achieved. Rational harmonic mode-locking technology is an improved scheme based on modulator mode-locking technology. In this paper, the rational number active mode-locking technology is studied, and the theoretical model of thulium-doped pulse laser with rational number active mode-locking is established. Through the theoretical simulation, the influence of the parameters of the mode-locked laser on the output pulse characteristics of the laser is analyzed. It is expected that on the basis of narrowing the pulse width of the output laser, the repetition rate of the pulse can be improved, so as to solve the problem of limiting the modulation frequency, and the ultra-short laser pulse of 2 渭 m band based on rational number active mode-locking can be obtained. The main work of this paper is as follows: 1. The numerical simulation model of rational number active mode-locked thulium-doped pulsed fiber laser is established. The simulation model is based on thulium-doped fiber amplifier model. The pulse transmission model and modulator model in ordinary single-mode fiber are composed of three parts. The role of three parts in the formation of 2 渭 band rational harmonic pulse laser is analyzed in detail. (2) the stability of 2 渭 m band pulse laser in time domain and frequency domain under different frequency doubling conditions is analyzed. The simulation results show that the mode-locked pulse with high repetition rate can be outputted with small modulation frequency. The modulation frequency used by the laser to output 18-fold frequency pulse in time domain is 3.6 times of fm= 3.6 fc, that is, 3.6 times of the fundamental frequency. The stability of the laser in frequency domain is analyzed. The results show that the stability of rational active mode locking technique is worse than that of ordinary active mode locking technique, and the stability decreases with the increase of order. The ultra-short pulse power, pulse width and energy parameters of an active mode-locked thulium-doped fiber laser with rational number vary with the length of active fiber, doping concentration, pump power and nonlinearity of single-mode fiber. The simulation results show that the output power increases linearly with the increase of doping concentration and the pulse width becomes narrower in the range of doping concentration of thulium ion. Increasing the length of thulium-doped fiber in a certain range can improve the output pulse power and reduce the pulse width effectively. The nonlinear effect of the ordinary single-mode fiber mainly affects the pulse width of the output pulse. The narrowest pulse width can be obtained by optimizing the length of the fiber. Increasing the pump power and the modulation depth of the modulator in a proper range can increase the power of the output laser pulse and facilitate the compression of narrow pulse width.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN248

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本文編號(hào)：2466259