高功率线偏振光纤激光技术研究

发布时间：2019-04-19 12:37

【摘要】：线偏振激光在激光通信、高精度传感、二次谐波产生、光学参量振荡、光束合成等领域有重要的应用价值。通常情况下,通过在激光系统中引入在线或空间偏振态选择器件可以获得线偏振激光。但是,引入偏振态选择器件存在插入损耗大,系统稳定性差,成本高,输出功率受限等问题。不含有偏振态选择器件的线偏振光纤激光器可以有效克服这些缺点,并有利于线偏振光纤激光器的全光纤化。目前,国内关于全光纤结构的高功率线偏振激光器的研究并不多见。本文结合实验室现有条件,在不引入偏振态选择器件的条件下,基于单一振荡器或主振荡功率放大(Master Oscillator Power Amplifier,简称MOPA)方案,以实现线偏振激光高功率、高效率、高消光比输出为目标,从理论和实验两个方面对高功率线偏振光纤激光技术进行了研究。首先,调研了国内外在线偏振光纤激光器方面的研究现状和进展,分析了四种类型线偏振光纤激光器的实现原理以及各自的特点,确定了适合采用全光纤结构并具备高功率输出潜力的线偏振振光纤激光器方案。其次,介绍了保偏光栅偏振模选择基本原理,实现了一台基于该原理的全光纤线偏振光纤激光振荡器,实现了42.3 W线偏振激光输出,消光比优于14 dB。对光栅的温度特性进行了测试和理论分析,实验研究和分析了光栅温度和偏振串扰对该线偏振光纤激光器输出特性的影响,指出了该类型线偏振光纤激光器的特点,提出了提高该类型激光器输出功率、改善该类型激光器输出特性的有效途径。同时,介绍了弯曲损耗偏振模选择基本原理,对熊猫型保偏光纤的弯曲损耗进行了数值仿真,实现了一台基于该原理的全光纤线偏振光纤激光振荡器,实现了93.2 W线偏振激光输出,消光比优于15.3 dB,这是目前国内基于该原理的线偏振光纤激光振荡器的最高输出功率。分析了该激光器的输出特性与弯曲损耗、光栅参数、光栅温度和偏振串扰的关系。对比分析了该类型激光器与基于保偏光栅偏振模选择原理的线偏振光纤激光振荡器的差异以及各自的优缺点,提出了改善和提升不含偏振态选择器件的全光纤线偏振光纤激光器输出特性的途径,对获得更高功率、更高消光比和稳定性更好的线偏振激光器具有一定的借鉴和指导意义。进一步,以基于弯曲损耗偏振模选择原理的线偏振光纤激光振荡器作为种子激光,采用一级MOPA方案,成功实现了线偏振光纤激光的高功率、高效率、高消光比、近衍射极限输出,最高输出功率1491 W,斜效率82.6%,消光比优于13.8dB,M2因子约为1.2,这是目前公开报道的线偏振光纤激光的最高输出功率。同时,采用考虑放大自发辐射和受激拉曼散射的速率方程模型,分析了该方案进一步提升功率的潜力。
[Abstract]:Linear polarization laser has important application value in the fields of laser communication, high precision sensing, second harmonic generation, optical parametric oscillation, beam synthesis and so on. In general, linear polarization laser can be obtained by introducing on-line or spatial polarization state selection devices into laser system. However, the introduction of polarization selection devices has many problems, such as large insertion loss, poor system stability, high cost and limited output power. Linear polarization fiber lasers without polarization state selection devices can effectively overcome these shortcomings and facilitate the all-fiber conversion of linear polarization fiber lasers. At present, there are few researches on high-power linear polarization laser with all-fiber structure in our country. In this paper, based on the single oscillator or main oscillation power amplifier (MOPA) scheme, the linear polarization laser with high power and high efficiency can be realized based on the existing conditions of the laboratory and without the introduction of the polarizing state selective device (Master Oscillator Power Amplifier,), which is based on the single oscillator or main oscillation power amplifier (MOPA). The technique of high power linear polarization fiber laser is studied both theoretically and experimentally for the purpose of high extinction ratio output. Firstly, the research status and development of on-line polarization fiber lasers at home and abroad are investigated, and the realization principles and characteristics of four types of linear polarization fiber lasers are analyzed. A linear polarization fiber laser with high power output potential and all fiber structure is determined. Secondly, the basic principle of polarization mode selection of polarization-maintaining grating is introduced, and an all-fiber linear polarization fiber laser oscillator based on this principle is realized. The output of 42.3 W linear polarization laser is realized, and the extinction ratio is better than 14 dB.. The effects of grating temperature and polarization crosstalk on the output characteristics of the linear polarization fiber laser are studied and analyzed experimentally. The characteristics of this type of linear polarization fiber laser are pointed out. An effective way to increase the output power and improve the output characteristics of this type of laser is presented. At the same time, the basic principle of polarization mode selection of bending loss is introduced. The bending loss of Panda polarization-maintaining fiber is simulated numerically, and an all-fiber linear polarization fiber laser oscillator based on this principle is realized. The output of 93.2 W linearly polarized laser is achieved, and the extinction ratio is better than 15.3 dB, which is the highest output power of the linear polarization fiber laser oscillator based on this principle. The relationship between the output characteristics of the laser and bending loss, grating parameters, grating temperature and polarization crosstalk is analyzed. The differences and advantages and disadvantages between this type of laser and linear polarization fiber laser oscillator based on polarization-maintaining grating polarization mode selection principle are compared and analyzed. This paper presents a way to improve and enhance the output characteristics of all-fiber linear polarization fiber laser without polarizing state selection device. It can be used for reference and guidance to obtain higher power, higher extinction ratio and better stability of linear polarization laser apparatus. Furthermore, the linear polarization fiber laser oscillator based on the principle of bending loss polarization mode selection is used as the seed laser, and the high power, high efficiency and high extinction ratio of the linear polarization fiber laser are successfully realized by using the first-order MOPA scheme. The maximum output power is 1491 W, the slope efficiency is 82.6%, the extinction ratio is better than 13.8dB, the M2 factor is about 1.2, which is the highest output power of linear polarization fiber laser reported. At the same time, a rate equation model considering amplified spontaneous emission and stimulated Raman scattering is used to analyze the potential of the scheme for further power enhancement.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24

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