基于石墨烯锁模的掺铒光纤激光器研究

发布时间：2018-03-25 07:20

本文选题：石墨烯　切入点：锁模　出处：《山东大学》2015年硕士论文

【摘要】：掺铒光纤激光器自上世纪八十年代诞生以来一直是光通信领域研究的热点,其输出特性经历了从连续运转到单纵模输出直至超快脉冲的产生等几个阶段,并在光纤通信、光纤传感、生物医疗等领域发挥着越来越重要的作用。具有超快脉冲输出特性的掺铒光纤激光器因其脉冲持续时间极短和峰值功率极高等特点近年来逐渐成为研究的热点。超快脉冲激光主要通过调Q和锁模技术来实现,其中被动锁模技术能产生皮秒乃至飞秒量级的超快脉冲且其系统结构简单而备受青睐。被动锁模是利用材料的非线性吸收或非线性相变的特性来产生激光超快脉冲,目前,比较成熟的非线性材料有半导体可饱和吸收镜和碳纳米管可饱和吸收体。但是制作半导体可饱和吸收镜需要相对复杂和昂贵的超净制造系统,这类器件的典型恢复时间约为几个纳秒,且半导体可饱和吸收镜的光损伤阈值很低,常用的半导体饱和吸收镜吸收带宽较窄。碳纳米管是一种直接带隙材料,带隙大小由碳纳米管直径和属性决定。不同直径碳纳米管的混合可以实现宽的非线性吸收带,覆盖常用的1.0-1.6μm激光增益发射波段。但是由于碳纳米管的管状形态会产生很大的散射损耗,提高了锁模阈值,限制了激光输出功率和效率。所以,研究人员一直在寻找一种具有高光损伤阈值、超快恢复时间、宽带宽和价格便宜等优点的饱和吸收材料。近年来研究者发现石墨烯由于它独特的零带隙结构,对所有波段的光都无选择性的吸收,且具有超快的恢复时间和较高的损伤阈值。因此利用石墨烯独特的非线性可饱和吸收特性将其制作成可饱和吸收体应用于被动锁模光纤激光器已经成为超快脉冲激光器研究领域的热点。本文正是基于将石墨烯可饱和吸收应用于掺铒光纤激光器来实现被动锁模开展了理论和实验研究,具体工作如下：简单介绍了掺铒光纤激光器的研究进展,对并掺铒光纤放大器和掺铒光纤激光器的理论基础做了分析。实验研究了掺铒光纤激光器的输出特性与泵浦源功率、增益光纤长度以及腔长等因素之间的对应关系。利用掺铒光纤荧光光源的光谱输出特性,找到了实验用掺铒光纤激光器的最佳增益光纤长度。在此基础上,介绍了光纤激光器的工作原理,开展了连续激光实验,得到了稳定的连续激光输出。分析了超快脉冲产生的机理,介绍了调Q技术和锁模技术实现超快脉冲输出的理论依据,同时对三种常见的可饱和吸收体,即半导体可饱和吸收镜、碳纳米管和石墨烯可饱和吸收体,从制作方法、制作成本、吸收带宽、损伤阈值、恢复时间和调制深度等几个方面的特性进行了对比。对石墨烯的能级结构及其独特的光电特性进行了系统的研究；分析了石墨烯的超快弛豫过程和可饱和吸收的相关机理；分析了石墨烯极低的电阻率的物理机制。利用化学气相沉积法制备了高质量的单层石墨烯薄膜并分别利用湿法和干法将石墨烯薄膜转移到光纤跳线氧化锆插芯的端面上,由于该过程是层数可控的,我们分别转移了一层、两层和六层到三个不同的光纤跳线氧化锆插芯的端面上,制成了三种层数不同的石墨烯可饱和吸收体并对其可饱和吸收特性进行了实验研究。实验研究了基于不同参数石墨烯可饱和吸收体的掺铒脉冲光纤激光器的光学输出特性,得到了皮秒量级的锁模输出脉冲串。建立石墨烯可饱和吸收体参数与锁模脉冲输出之间的对应关系,并对激光腔的参数进行了优化。
[Abstract]:Erbium doped fiber laser has been a hot research topic in the field of optical communication since the last century, was born in 80s, the output characteristics of experience from the continuous operation to single longitudinal mode output until the ultrafast pulse generation in several stages, and in optical fiber communication, optical fiber sensing, biomedical and other fields play an increasingly important role. With fast the pulse output characteristics of erbium doped fiber laser because of its extremely short pulse duration and high peak power has gradually become the research hotspot in recent years. Mainly through regulating Q ultrafast pulsed laser and mode-locked technology to realize, which passively mode-locked technology can produce picosecond and femtosecond laser pulse and the system has the advantages of simple structure and favored passive mode locking is. The nonlinear absorption properties of materials or nonlinear by the phase transformation to produce laser ultrafast pulses, the nonlinear material of mature half The conductor saturable absorption mirror and carbon nanotubes SATURABLEABSORBER. But the production of semiconductor saturable absorption mirror requires relatively complicated and expensive ultra clean manufacturing system, typical of this kind of device recovery time is about several nanoseconds, and a semiconductor saturable absorber mirror optical damage threshold is very low, the commonly used semiconductor saturable absorber mirror with narrow absorption bandwidth. The carbon nanotube is a kind of direct band gap material, the band gap size by the diameters of carbon nanotubes and attribute decision. To achieve a wide nonlinear absorption band of carbon nanotube can be mixed with different diameters, covering 1.0-1.6 m laser used to gain emission band. But due to the tubular morphology of carbon nanotubes will produce large scattering loss, improve the mode locking threshold, limit the laser output power and efficiency. Therefore, researchers have been looking for a high optical damage threshold, ultrafast recovery time, bandwidth and price is Should the advantages of saturated absorption materials. In recent years, the researchers found that graphene due to its unique zero band gap structure of all bands of light selective absorption, and has a fast recovery time and high damage threshold. So the nonlinear graphene unique saturable absorption to produce a saturable the absorber used in passively mode-locked fiber laser has become the research focus in the field of ultrafast pulsed laser. This paper is based on the graphene saturable absorber used in erbium-doped fiber laser to realize passive mode-locked carried out theoretical and experimental research, the specific work is as follows: This paper introduces the research progress of erbium doped fiber laser, the based on theoretical analysis and erbium-doped fiber amplifier and erbium-doped fiber laser. Experimental study on the output characteristics and pump power erbium-doped fiber laser, gain fiber The relationship between length and cavity length and other factors. The spectral output characteristics of erbium-doped fiber, find the best gain fiber length of erbium doped fiber laser experiments. On this basis, introduces the working principle of the fiber laser, the CW laser experiment, obtained the continuous stable output analysis. The mechanism of ultrafast pulse generation, introduces Q technology and mode locking technology to achieve ultra fast pulse output theory, at the same time, three kinds of saturable absorber, namely SESAM, carbon nanotubes and graphene saturable absorber, from the production method, production cost, absorption bandwidth, damage threshold compared the recovery time and the modulation depth of the characteristics of several aspects. The energy level structure of graphene and its unique optoelectronic properties were studied; the analysis of ultrafast graphene The relaxation process and mechanism of saturable absorption; analysis of the physical mechanism of low resistivity graphene. By chemical vapor deposition of the graphene film of high quality and are using wet and dry graphene film transfer to zirconia fiber jumper ferrule end face, because this process is the number of controllable, we transfer a layer, surface layer and the six layer two to three different optical fiber jumper zirconia core insert on graphene layers made of three kinds of different saturable absorber and the saturable absorption properties were experimentally studied. Experimental study on the optical output characteristics of erbium doped the different parameters of the graphene saturable absorber pulse fiber laser based on the mode-locked output pulse on picosecond. Establish the corresponding relationship between the graphene can be saturated absorber parameters and mode-locked pulse output The parameters of the laser cavity are optimized.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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