【作者】 栗剑；

【导师】 宋晏蓉；

【作者基本信息】 北京工业大学 ， 物理学， 2013， 硕士

【摘要】 在科技飞速发展的当今社会，科研和工业生产中需要激光器产生更高的脉冲能量和更窄的脉冲宽度，这使得激光器调Q技术得到快速发展。调Q激光器在遥感、医学、激光雷达、激光精密测量等领域都有广泛的应用。碳纳米管作为可饱和吸收体，其吸收大小可以由膜厚度来控制，吸收峰的位置可以由碳纳米管的直径来控制，而吸收带宽取决于纳米管的直径分布，具有很好的可饱和吸收特性。此外碳纳米管可饱和吸收体相对于目前使用较多的半导体可饱和吸收体而言，易于制作、成本低廉。正是由于其具有如此优良的特性，使得科学家们对其展开了广泛的研究，因此研究碳纳米管在脉冲激光器中的应用具有实用价值。本论文主要的研究内容有：(1)对调Q激光器的原理进行了分析，讨论了品质因数Q对于调Q激光器的影响，给出了调Q激光器对光泵浦速率、谐振腔Q值和增益介质的参数要求。通过求解调Q激光器的速率方程，得到了峰值功率Pm、腔内光子数Ф、输出能量E以及调Q脉冲的宽度等参数。(2)研究了Nd:YCOB晶体的性质，研制了使用透射式单壁碳纳米管作为可饱和吸收体的Nd:YCOB固体被动调Q激光器。通过搭建V型腔，得到了输出波长稳定的调Q激光脉冲。讨论了泵浦功率对于输出功率、脉冲宽度和脉冲重复频率的影响。(3)研究了掺Yb3+光纤的性质，研制了使用单臂碳纳米管薄膜作为可饱和吸收体被动调Q掺Yb3+光纤激光器。通过使用环形腔设计，得到了波长为1033.44nm和1040.39nm的调Q激光输出。并且得到了脉冲宽度、脉冲重复频率及输出功率与泵浦功率的关系。(4)研究了光子晶体光纤在调Q激光器中的波长选择作用。通过平面波展开法计算了光子晶体的带隙。分析了空气孔间距、空气填充比、空气孔直径和介质折射率对于光子晶体光纤带隙的影响。运用光束传播法模拟了带隙型光子晶体光纤的导光特性。设计了两种光子晶体光纤，使Yb3+光纤激光器产生单波长输出。更多还原

【Abstract】 With the rapid development of science and technology, scientific research andindustrial productions require laser have higher pulse energy, and more narrow pulsewidth, which improved the laser Q-switched technique. Q-switched laser has beenwidely used in remote sensing, medical, laser radar, laser precision measurement etc.As a saturable absorber, the absorption intensity can be controlled by the membranethickness. The absorption peak position and absorption bandwidth can be controlledby the diameter and the diameter distribution of the carbon nanotubes. In addition,compared with the semiconductor saturable absorber, carbon nanotube saturableabsorber is more easy manufacture and low cost. As it has such excellent properties,scientists have carried out extensive research on its. In this paper, the main contentsare as follows:(1) Made a detailed analysis on the Q-switched laser theory，and discussed theinfluence of the quality factor Q on a Q-switched laser. Achieved the parameters ofthe pump rate, Q value and gain material for Q-switched lasers. By solving the rateequations, the peak power(Pm)，cavity photon number(Ф),output energy(E) and pulsewidth of the Q-switched laser have been obtained.(2) The properties of Nd:YCOB crystal is discussed, and a passively Q-switchedNd:YCOB laser with a single-walled carbon nanotube saturable absorber is beendemonstrated. The transmission-type SWCNT–SA is used in a V-type cavity. Wemeasured the spectrum diagram at different pump powers to test the system stability.The effects of the output power, the pulse width and pulse repetition frequency on thepump power were obtained.(3) The properties of Yb3+doped fiber is discussed, and a Yb3+doped fiber laserwith a single-walled carbon nanotube saturable absorber is been reached. In theexperiment, we achieve the output wavelength at both1033.44nm and1040.39nm inthe Q-switched laser. The effects of the output power, the pulse width and pulserepetition frequency on the pump power were obtained.(4) The characteristics of the wavelength selection of a photonic crystal fiber isdiscussed. By using it, we could get a single wavelength laser in the Yb3+doped fiberQ-switched laser. According to the Maxell’s equations of electromagnetic wave，theband gap is simulated which based on the plane waves expansion method(PWM).The capability of light guiding is simulated by beam propagation method(BPM). Theeffects of the air hole diameter, air hole filling ratio, the air hole distance andrefractive index of the medium on the band gap photonic crystal fiber is simulated.Two kinds of bandgap photonic crystal fibers were designed, which could be used tomake the Yb3+doped fiber laser to get a single wavelength output laser.更多还原