通过脉冲动力学优化提升光子晶体光纤飞秒激光性能的研究

发布时间：2018-03-22 23:29

本文选题：飞秒激光　切入点：高平均功率　出处：《天津大学》2016年博士论文　论文类型：学位论文

【摘要】：超短脉冲激光在基础科研、工业加工等领域具有重要应用,使得输出高平均功率、高脉冲质量和高光束质量的光纤飞秒激光成为近些年来超短脉冲激光领域重要的研究方向之一。本文通过优化动力学过程,提升飞秒激光器和放大系统的输出性能,主要利用多芯光子晶体光纤为切入点构建放大系统,并对多芯光子晶体光纤进行模式选取和非线性方面的研究,进而将高功率飞秒激光应用于超连续谱的产生中。本论文的主要工作概括如下:1:建立了多芯光子晶体光纤多横模运转的速率方程,提出带有掺杂分布的七芯光子晶体光纤的新设计结构,将输出同相位超模功率占总功率的百分比从19%提高至70%,实现了多横模运转中同相位超模主导输出。2:实验研究了基于18芯光子晶体光纤的非线性放大系统,输出平均功率高达110 W且脉冲宽度83 fs的飞秒激光,是多芯光子晶体光纤激光放大系统输出的最高平均功率记录。利用光栅和滤波器组成的预整形装置优化脉冲在放大系统中的动力学过程,使得输出平均功率20 W-110 W之间的脉冲均能被压缩至百飞秒以下。3:实验研究了高峰值功率脉冲入射下,在18芯光子晶体光纤中非线性效应与输出光斑模式的变化关系。分析了入射脉冲平均功率、泵浦功率对于输出光斑模式的影响,同时利用滤波器观测不同波段光谱对应的横模模式,实现了对于多芯光子晶体光纤超模模式非线性耦合的探索。4:建立了再生放大器的数值模型,讨论了入射脉冲峰值功率、脉冲宽度和放大腔内滤波器带宽对输出脉冲的影响;实验搭建了光纤再生放大器,实现了入射脉冲13个腔内循环的稳定运转,输出放大脉冲能量20 nJ,光谱宽度约为60 nm的脉冲。5:研究了高功率飞秒激光在带隙光子晶体光纤跨带隙产生超连续谱的动力学过程,在产生560 nm-1470 nm的超连续光谱过程中,激光能量不仅在带隙间流动,也在不同模式间流动。首次在多芯光子晶体光纤中实现超连续谱的产生,获得平均功率5.4 W,输出波长500 nm-1700 nm的宽带超连续谱,研究还发现短光纤的输出光斑模式为超模的叠加态而利用长光纤则可获得同相位超模运转。
[Abstract]:Ultrashort pulse lasers have important applications in basic scientific research, industrial processing and other fields, resulting in high average power output. Fiber femtosecond laser with high pulse mass and high beam quality has become one of the important research directions in the field of ultrashort pulse laser in recent years. In this paper, the output performance of femtosecond laser and amplification system is improved by optimizing the dynamic process. The amplification system is constructed by using multi-core photonic crystal fiber as the starting point, and the mode selection and nonlinear aspects of the multi-core photonic crystal fiber are studied. Furthermore, the high power femtosecond laser is applied to the generation of supercontinuum spectrum. The main work of this thesis is summarized as follows: the rate equation of multi-transverse mode operation of multi-core photonic crystal fiber is established. A new structure of seven-core photonic crystal fiber with dopant distribution is proposed. The in-phase supermode power is increased from 19% to 70% of the total power, and the in-phase supermode dominant output. 2. The nonlinear amplification system based on 18-core photonic crystal fiber is experimentally studied. Femtosecond laser with an average power of 110 W and a pulse width of 83 fs, It is the highest average output power record of multi-core photonic crystal fiber laser amplification system. The dynamic process of pulse in amplification system is optimized by a preshaping device composed of grating and filter. So that the average output power of 20 W-110 W pulse can be compressed to less than 100 femtosecond. 3. The experimental study of high peak power pulse incident, The relationship between the nonlinear effect and the mode of output spot in 18-core photonic crystal fiber is analyzed. The influence of the average power of incident pulse and pump power on the mode of output spot is analyzed. At the same time, the filter is used to observe the transverse mode mode corresponding to the spectrum of different bands. The exploration of nonlinear coupling of supermode in multi-core photonic crystal fiber is realized. The numerical model of regenerative amplifier is established, and the peak power of incident pulse is discussed. The effect of pulse width and filter bandwidth on the output pulse is studied, and the optical fiber regenerative amplifier is constructed, which can realize the steady operation of 13 intracavity cycles of the incident pulse. Output amplified pulse energy of 20 nJ, spectral width of about 60 nm pulse. 5. The kinetic process of high power femtosecond laser producing supercontinuum spectrum across bandgap photonic crystal fiber is studied. In the process of producing supercontinuum spectrum at 560 nm-1470 nm, the output pulse energy is 20 nJ and the spectral width is about 60 nm. The laser energy flows not only between band gaps but also between different modes. For the first time, the generation of supercontinuum spectrum is realized in multi-core photonic crystal fiber. The average power is 5.4 W and the output wavelength is 500 nm-1700 nm. It is also found that the output spot mode of short fiber is supermode superposition state, and the same phase supermode operation can be obtained by using long fiber.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN24;TN253

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