【作者】 周仁来；

【导师】 鞠有伦；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2013， 博士

【摘要】 2μm激光处于大气透明窗口和人眼安全波段，被广泛的应用于激光遥感、激光医疗和材料加工等领域，其中2μm脉冲激光器是获得3⁵μm中红外波长参量振荡输出理想泵浦源。和2μm固体激光器相比，全光纤掺Tm³⁺脉冲激光器具有结构紧凑和抗干扰能力强等优点，但受到器件工艺等因素限制，关于全光纤掺Tm³⁺脉冲激光器及放大器的研究鲜有报道。本论文以获得2μm全光纤掺Tm³⁺脉冲激光器，并将其作为种子源进行全光纤掺Tm³⁺脉冲放大器的探索研究作为基本出发点，分别从理论和实验方面详细研究了带内泵浦的增益开关掺Tm³⁺光纤激光器激光特性以及全光纤掺Tm³⁺脉冲放大器的输出特性，期望为相关领域发展做出一定贡献。理论方面，首先在考虑功率重叠因子和Stark能级分裂情况下，建立带内泵浦的掺Tm³⁺光纤激光器速率方程理论模型，推导出了反转粒子数、腔内光子数、阈值能量、脉冲提取效率等解析式，并在此基础上对激光器的上能级粒子数、腔内光子数、脉冲建立时间、脉冲宽度等参数时间特性进行研究；文中还建立掺Tm³⁺光纤激光器的行波方程理论模型，讨论了上能级粒子数、腔内光子数沿光纤轴向变化情况，并研究了腔内可提取能量和激光器功率输出特性。其次，在考虑ASE对LMA高掺杂光纤放大器输出特性影响的基础上，建立了掺Tm³⁺光纤放大器的速率方程理论模型，分别对其在稳态放大和脉冲放大情况下进行数值仿真。在稳态放大情况下，研究了上能级粒子数、泵浦光和ASE沿光纤轴向分布情况；在一定泵浦功率下，分析了种子光功率和增益光纤长度对放大器功率输出特性的影响；在脉冲放大情况下，研究了不同重频和泵浦功率下，上能级粒子数和ASE沿光纤轴向分布情况，分析了脉冲输出能量和光纤存储能量随时间变化情况，以上理论分析为掺Tm³⁺光纤放大器实验研究奠定基础。实验方面，首先进行了1558nm双级脉冲掺Er³⁺光纤放大器实验研究，分别对每级放大器的输出能量、ASE功率和输出光谱进行详细测量和分析，讨论了ASE抑制与滤除方法。进行了800nm飞秒激光器刻写大芯径多模FBG的实验研究，通过在线监测激光器输出功率与刻写FBG辐射时间的变化关系，并结合掺Tm³⁺光纤激光器速率方程模型对FBG反射率和纤芯折射率调制等光栅参数进行估算；进行了紫外曝光法刻写了单模FBG实验研究，并使用宽带光源和高精度OSA对FBG光谱特性进行了研究，获得了中心波长相同，反射率不同的FBG。利用1558nm掺Er³⁺脉冲放大器作为泵浦源和单模FBG作为输入输出镜，进行了全光纤增益开关掺Tm³⁺光纤激光器实验，详细研究激光器的输出功率、脉冲宽度和脉冲建立时间。其次利用空间耦合方式将2054nm Q开关Tm,Ho:YVO4脉冲光耦合入LMA掺Tm³⁺光纤中进行脉冲放大实验，研究了放大器的输出功率、转换效率、光谱特性、光束质量因子、光斑分布情况和放大脉冲波形畸变情况。最后将实验研究的增益开关掺Tm³⁺光纤激光器作为种子源，进行了全光纤掺Tm³⁺脉冲放大器的实验研究，详细测量和分析了放大器输出功率、光谱特性、光束质量因子、光斑分布以及放大脉冲波形情况，最后指出ASE功率积累、寄生振荡和自脉冲效应是影响放大器能量输出的主要因素。更多还原

【Abstract】 2μm lasers which locate in atmospheric transmission window and eye-saferange, are being widely used in the field of laser remote sensing, medical andmaterial processing. In addition,2μm pulsed lasers are excellent pump sourcesobtaining Middle-infrared3⁵μm optical parametric oscillation lasers. Comparedwith2μm solid lasers, all-fiber pulsed Tm³⁺-doped fiber lasers have advantages ofcompact structure and strong anti-interference capability. However, due to thelimition of fiber device technology, all-fiber pulse Tm³⁺-doped fiber lasers andamplifiers are few reported. This thesis investigates the band pumped gain-switched Tm³⁺-doped fiber laser characteristics theoretically and experimentally,in which all-fiber2μm pulse Tm³⁺-doped laser and amplifier with the pulse laseras injected seed laser are taken as the basic starting point. The outputcharacteristics of pulse Tm³⁺-doped fiber amplifier are investigated in detailed.We expect to make some contribution to the development of related fields.Theoretically, the band-pumped Tm³⁺-doped fiber laser rate equation modelis established with power overlapping factor and Stark energy level considered.The expressions of inversion population, intracavity photon density, thresholdenergy, and pulse extraction efficiency are derived. Time characteristic of upper-level population, cavity photo density, pulse built-time and pulse width arediscussed on this basis meanwhile. In addition, the traveling-wave equations ofTm³⁺-doped fiber laser are also established. The change of upper level populationand cavity photo density along fiber axis are discussed, as well as the extractableenergy and output power. Secondly, taking into account the influence of ASEabout LMA highly doped fiber amplifier output characteristics, we established theTm³⁺doped fiber amplifier rate equation model and studied the steady-stateamplification and pulse amplification numerically. In steady-state mode, the upperlevel population, pump light and ASE light distributing along the fiber axis areinvestgated, and the output characteristics of amplifier are also investigated indifferent injection power. In pulse amplification mode, the upper level population,the pump light and ASE light distributing along the fiber axis are investgated, therelationship between output pulse energy, storage energy and repetition rate arealso analysed, establishing a good foundation for next experimental study.Experimentally, the1558nm two stages Er³⁺doped pulse amplifier wasstudied in detailed. The output energy, ASE power and output spectra weremeasured and analysed. The relationship of ASE and amplifier output power wasalso discussed. The experiment of large core double-cladding FBG inscribed by 800nm fs laser was investigated. The output power variation during the process ofinscribing FBG was recorded. Combined to the Tm³⁺-doped fiber laser rateequation model, the FBG reflectivity and the core refractive index modulation areanalysed. The experiment of single mode FBG inscribed by UV exposure methodwas investigated, and the spectra characteristic are measured by a broadband lightsource and high-resolution OSA. The experiment of all fiber gain-switched Tm³⁺-doped fiber laser was investgated, in which the laser output power, pulse widthand pulse built-time were studied. Secondly, the2054nm Q-switchedTm,Ho:YVO4pulse laser was coupled into the core of LMA Tm³⁺-doped fiber.The output power, conversion efficiency, output wavelength, beam quality factor,spot distribution and amplified pulse waveform distortion were all discussed indetailed. The gain-switched1940nm laser was injected into highly Tm³⁺-dopedfiber as a seed laser. The output characteristics of all fiber pulse amplifier werestudied, the output power, peak power, output wavelength, beam quality factor,spot distribution, and the amplified output pulse waveform parameters weremeasured and analysed. The ASE light, parasitic oscillation and self-pulsing effectwere the main reason which influence the amplifier output.更多还原