线形腔锁模掺镱光纤激光器研究

发布时间：2018-01-04 21:31

本文关键词：线形腔锁模掺镱光纤激光器研究　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：与环形腔相比,线形腔被动锁模光纤激光器的谐振腔内无需连接环形器或者隔离器,具有结构简单、成本低、易于集成等优点。目前,基于可饱和吸收体(单壁碳纳米管、石墨烯、拓扑绝缘体、黑磷及半导体可饱和吸收镜SESAM等)、光纤非线性效应(非线性光纤环形镜NOLM、非线性偏振旋转效应NPR、非线性光纤放大镜NALM等)以及自锁模原理的线形腔锁模光纤激光器已有报道。其中SESAM是技术成熟、应用广泛的一种锁模器件,能够获得纳秒乃至飞秒级激光脉冲,然而SESAM的结构复杂,而且制作成本高。基于可饱和吸收体的线形腔锁模光纤激光器的相关报道很少,绝大多数是采用透射式锁模,这使得可饱和吸收体很容易受到热损伤的影响,从而限制了高能量锁模脉冲的输出。NOLM的实现只需将一个2x2光耦合器的两个输出端口连接起来即可,在制作方面更加简单。自锁模光纤激光器实现脉冲激光不依赖外部锁模器件,通过对其脉冲行为的研究,有助于进一步理解光纤激光器的自锁模产生机制及其性能控制方法。本论文设计制作基于非线性光纤环形镜的线形腔锁模掺镱光纤激光器和自锁模掺镱光纤激光器,研究了光纤激光器的脉冲输出特性,对它们的相关特性进行了理论和实验分析。本论文的主要工作如下:1、对线形腔被动锁模光纤激光器的主要类型及其运转机理进行了简要介绍和分析,概述了各种类型锁模光纤激光器近期的研究进展及现状。2、基于掺镱光纤速率方程,分析了光纤激光器中增益行为及特性。基于广义非线性薛定谔方程,建立了线形腔光纤激光器中超短脉冲的传输模型,理论分析了自相位调制、群速度色散以及三阶色散对光脉冲在光纤中演化过程的影响。模拟并分析了在不同谐振腔长度、不同掺镱光纤长度以及不同可饱和吸收系数情况下,光脉冲在光纤中稳定传输时其频域和时域的变化规律。3、开展了基于NOLM的线形腔锁模掺镱光纤激光器的实验研究,测试了不同长度环形镜的脉冲输出特性,分别获得了调Q,调Q锁模以及锁模激光脉冲,并对激光脉冲的产生阈值、能量及脉冲宽度等特性进行了分析。4、研究了线形腔单包层掺镱光纤激光器和环形腔双包层掺镱光纤激光器的自锁模行为及特性。自锁模光纤激光器中未加入偏振控制器件。在线形腔单包层掺镱光纤激光器实验中,通过改变谐振腔的长度,分别实现了自调Q,自调Q锁模以及自锁模脉冲输出。而在环形腔自锁模双包层掺镱光纤激光器中,通过控制泵浦功率的大小,分别获得了亮脉冲、亮暗脉冲对及暗脉冲,并对环形腔自锁模双包层掺镱光纤激光器的自脉冲向连续波的过渡现象进行了分析和讨论。
[Abstract]:Compared with the ring cavity, the linear cavity passive mode-locked fiber laser does not need to connect ring or isolator in the resonator, which has the advantages of simple structure, low cost, easy integration and so on. Based on saturable absorbers (single walled carbon nanotubes, graphene, topological insulators, black phosphorus and semiconductor saturable absorbers SESAM, etc.), optical fiber nonlinear effect (NOLM). Nonlinear polarization rotation effect, nonlinear fiber magnifying glass (NALM, etc.) and self-mode-locking principle of linear cavity mode-locked fiber lasers have been reported. Among them, SESAM is a mature technology. A widely used mode-locking device can obtain nanosecond and even femtosecond laser pulses, but the structure of SESAM is complex. There are few reports about linear cavity mode-locked fiber lasers based on saturable absorbers, most of which are transmission mode locking, which makes saturable absorbers vulnerable to thermal damage. This limits the output of high energy mode-locked pulse. NOLM can only be achieved by connecting two output ports of a 2x2 optical coupler. The self-mode-locked fiber laser is independent of the external mode-locking device, and its pulse behavior is studied. In this paper, we design and fabricate the linear cavity mode-locked ytterbium-doped fiber laser and self-mode-locked ytterbium-doped fiber laser based on nonlinear fiber ring mirror. The device. The pulse output characteristics of fiber lasers are studied, and their related characteristics are analyzed theoretically and experimentally. The main work of this thesis is as follows: 1. The main types and operating mechanism of linear cavity passive mode-locked fiber lasers are briefly introduced and analyzed. The recent research progress and present situation of various types of mode-locked fiber lasers are summarized. Based on the rate equation of ytterbium-doped fiber, the gain behavior and characteristics in fiber laser are analyzed. Based on the generalized nonlinear Schrodinger equation, the transmission model of ultrashort pulse in linear cavity fiber laser is established. The effects of self-phase modulation, group velocity dispersion and third-order dispersion on the evolution of optical pulses in optical fiber are analyzed theoretically. Under different ytterbium-doped fiber lengths and different saturable absorption coefficients, the frequency and time domain variations of optical pulse in stable transmission in fiber are obtained. 3. The experimental study of linear cavity mode-locked ytterbium-doped fiber laser based on NOLM is carried out. The pulse output characteristics of ring mirror with different lengths are tested. The Q-switched, Q-switched mode-locked and mode-locked laser pulses are obtained respectively. The generation threshold, energy and pulse width of laser pulse are analyzed. 4. The self-mode-locking behavior and characteristics of linear cavity single-clad ytterbium-doped fiber laser and ring cavity double-clad ytterbium-doped fiber laser are studied. No polarization controller is added to the self-mode-locked fiber laser. In the laser experiment. By changing the length of the resonator, the self-Q-switched mode-locking and self-mode-locked pulse output are realized, respectively. In the ring cavity self-mode-locked double-clad ytterbium-doped fiber laser, the pump power is controlled. Bright pulse, bright dark pulse pair and dark pulse are obtained, and the transition from self pulse to continuous wave of ring cavity self-mode-locked double-clad ytterbium-doped fiber laser is analyzed and discussed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN248

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