基于硫化钨可饱和吸收体掺铒光纤激光器研究

发布时间：2018-08-19 12:20

【摘要】：被动锁模光纤激光器不仅拥有非常窄的脉冲宽度、极高的峰值功率及宽的光谱,而且具有成本低廉、结构紧凑、无需调试及效率高等优势,使得其在超快诊断、飞秒加工、生物医学及激光雷达等领域具有非常广泛的应用前景。随着纳米技术及新材料的不断发展,新型二维材料用于光纤激光器被动锁模已经成为当前激光领域的一个重要焦点。继单壁碳纳米管、石墨烯及拓扑绝缘体之后,新型二维材料过渡金属硫化物近年来引起科学家们强烈的兴趣。二硫化钨(Tungsten Disulfide,WS_2)作为过渡金属硫化物中比较有代表性的一种材料也受到极大的关注。WS_2优异的电学和光学的特性如超快的恢复时间和超宽带的饱和吸收等,使其在超快激光方面拥有非常广泛的应用前景。本论文以新型二维材料WS_2被动锁模掺铒光纤激光器为研究平台,实验上探索基于WS_2材料锁模新器件的应用价值。本论文的主要工作内容如下:1.介绍了被动锁模光纤激光器的研究进展,并详细介绍了被动锁模技术的几种方式如非线性偏振旋转(Nonlinear Polarization Rotation,NPR)锁模技术、“8”字腔锁模技术、碳纳米管和石墨烯、新型二维纳米材料等。2.分析了WS_2材料的基本能带结构,描述了WS_2饱和吸收的基本过程和原理。对激光锁模脉冲形成机制做了理论分析,概括了影响激光锁模的几个关键因素。3.运用脉冲激光沉积法(Pulsed Laser Deposition,PLD)法制备WS_2可饱和吸收体(Saturable Absorber,SA),在实验中SA的饱和吸收特性表现出厚度相关性,且SA器件具有较低的插入损耗(Insertion Loss,IL)和良好的功率承受能力。在掺铒光纤激光器中,泵浦功率为54 mW时实现了稳定的基频锁模激光输出,脉冲的持续时间为675 fs,信噪比达65 dB。在395 mW的最大泵浦功率下,脉冲持续时间缩短到452 fs而信噪比也达到48 dB。此时高阶谐波锁模的重复频率为1.04 GHz,对应于53阶谐波。4.将WS_2纳米片分散液填充到单模光子晶体光纤(Photonic Crystal Fibers,PCF)中,制备一种超精细的可饱和吸收体。通过对SA进行表征,测得可饱和吸收体的调制深度、饱和强度及非饱和损耗分别为3.53%、159 MW/cm2和23.2%。基于制备好的精细SA,搭建了一个掺铒光纤(Er-doped Fiber,EDF)激光器平台以检验所制备的可饱和吸收体的锁模性能。实验中,EDF激光器实现了激光锁模并获得了524 fs脉冲输出和19.57 MHz的重复频率,脉冲的信噪比(Signal to Noise Ratio,SNR)达60.5dB。5.介绍了光纤集成型WS_2-SAM的具体结构、制备方法及在掺铒光纤线形激光器中的锁模特性。通过搭建一套掺铒光纤线形激光器对制备样品的锁模特性进行了表征。实验结果表明在搭建的掺铒光纤激光器中WS_2-SAM能够实现激光自锁模。锁模脉冲受到Q调制的影响,实验中测得的调Q脉冲的信噪比为40 dB。实验证明这种器件用于实现激光锁模的可行性,且后期具有很大的优化空间。
[Abstract]:Passive mode-locked fiber laser not only has very narrow pulse width, extremely high peak power and wide spectrum, but also has the advantages of low cost, compact structure, no need of debugging and high efficiency. Biomedicine, lidar and other fields have a very wide range of applications. With the development of nanotechnology and new materials, the application of new two-dimensional materials in passive mode-locking of fiber lasers has become an important focus in the field of lasers. Following single-walled carbon nanotubes, graphene and topological insulators, transition metal sulfides, a new two-dimensional material, have attracted great interest in recent years. As a representative material of transition metal sulfides, Tungsten disulfide has attracted great attention. WS2 has excellent electrical and optical properties such as ultra-fast recovery time and ultra-wideband saturation absorption. It has a very wide application prospect in ultra fast laser. In this paper, a novel two-dimensional WS_2 passive mode-locked erbium-doped fiber laser is used as the research platform, and the application value of the new device based on WS_2 is explored experimentally. The main work of this thesis is as follows: 1. The research progress of passive mode-locked fiber laser is introduced. Several methods of passive mode-locking such as nonlinear polarization rotation (Nonlinear Polarization rotation NPR mode-locking, "8" word cavity mode-locking, carbon nanotubes and graphene are introduced in detail. New two-dimensional nanomaterials, etc. The basic band structure of WS_2 material is analyzed and the basic process and principle of WS_2 saturation absorption are described. The mechanism of laser mode-locking pulse formation is theoretically analyzed, and several key factors affecting laser mode-locking are summarized. WS_2 saturable absorbers (Saturable Absorber SA) were prepared by pulsed laser deposition (Pulsed Laser deposition) method. In the experiment, the saturation absorption characteristics of SA show a thickness correlation, and the SA devices have low insertion loss (Insertion osssil) and good power tolerance. In Erbium-doped fiber laser, stable fundamental frequency mode-locked laser output is achieved when the pump power is 54 MW. The duration of the pulse is 675 fs and the signal-to-noise ratio (SNR) is 65 dB. At the maximum pump power of 395 MW, the pulse duration is reduced to 452 fs and the SNR is 48 dB. The repetition rate of higher order harmonic mode-locking is 1.04 GHz, corresponding to 53rd order harmonic. 4. A kind of hyperfine saturable absorber was prepared by filling the dispersion of WS_2 nanoscale into (Photonic Crystal Fibers crystal fiber (PCF). Through the characterization of SA, the modulation depth, saturation intensity and unsaturated loss of the saturable absorber were measured to be 3.53 ~ 159 MW/cm2 and 23.2 MW/cm2, respectively. Based on the prepared fine SAs, an erbium-doped fiber (Er-doped) laser platform was built to test the mode-locking performance of the saturable absorber. In the experiment, the laser mode-locking is realized and the output of 524fs pulse and the repetition rate of 19.57 MHz are obtained. The signal-to-noise ratio (SNR) of the pulse is 60.5 dB.5. The structure, preparation method and mode-locking characteristics of fiber integrated WS_2-SAM in erbium-doped fiber linear lasers are introduced. A set of erbium-doped fiber linear lasers was constructed to characterize the mode-locking characteristics of the prepared samples. The experimental results show that WS_2-SAM can realize self-mode-locking in the erbium-doped fiber laser. Mode-locked pulse is affected by Q-modulation. The signal-to-noise ratio of Q-switched pulse measured in the experiment is 40 dB. The experimental results show that this device is feasible for laser mode-locking and has a large space of optimization in the later stage.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN248

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