温度不敏感激光技术及单频双脉冲混合MOPA系统的研究
文献类型：学位论文
| 作者 | 魏大康 |
| 学位类别 | 硕士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 朱小磊 |
| 关键词 | Nd:YAG，六边形板条，温度不敏感，调Q，MOPA，单频 |
| 其他题名 | Research on Temperature Insensitive Laser Technology and Single-frequency Double-pulse Hybrid MOPA System |
| 中文摘要 | 体积小、携带方便、低功耗、转换效率高的温度不敏感的全固态激光器在便携式激光设备和激光雷达方面都有着非常重要的应用前景，尤其是在人眼安全激光测距、激光指示器以及3D激光雷达系统等领域的应用。此外，高能量、单频特性良好的双脉冲1064nm激光在雷达系统中具有重要的需求，可以作为获得1.57μm单频双脉冲OPO/OPA系统的泵浦源，而1.57μm单频激光是作为探测二氧化碳浓度的差分吸收雷达系统的重要光源之一。本文的研究工作主要从温度不敏感激光技术和高能量单频双脉冲激光源两个方面展开。 在温度不敏感激光技术方面的研究工作包括了理论和实验研究两部分。首先对温度不敏感激光技术的发展现状进行了概述，介绍了减缓泵浦光的波长温漂、采用吸收谱宽的材料以及增大泵浦光吸收路径等三种实现激光器温度不敏感的基本方法。该激光器是基于激光二级管泵浦Nd:YAG六边形板条结构来实现宽温度范围工作。泵浦光采用定制的激光二极管阵列，它们由三种不同波长间隔排列组成，这样可以有效降低温漂的影响。通过理论仿真发现，当掺杂浓度为1.0 atm%时，Nd:YAG增益介质吸收长度大于46mm时，增益介质对808nm泵浦光的吸收效率在-30℃~70℃温度范围内都能大于93%。根据仿真结果和几何学原理，完成了六边形板条结构的设计。谐振腔采用的是对温度和振动不敏感的正交Porro棱镜的偏振耦合输出腔。实验研究部分主要包括了平平腔实验，准连续输出实验以及正交Porro棱镜腔的调Q输出初步实验。激光器在实际9℃~45℃的温度变化范围内调Q运转时，最大输出脉冲能量约为112.4mJ，光-光转换效率约为13.8%，斜率效率达到22.7%，在这个温度范围内，不考虑泵浦LD输出能量的波动校正，调Q脉冲输出能量RMS值为6.03mJ，最大能量波动为8.40%，此时的激光脉冲宽度大致为14.3ns，输出光斑约为5.0mmx5.0mm方形光斑，输出激光的发散角全角约为3mrad。输出激光x和y方向光束质量因子分别为: Mx2=19.2, My2=23.9。 混合MOPA系统是一种获得高能量单频激光脉冲输出的有效方法，它既结合了光纤放大器转换效率高，光束质量好等优点，同时又发挥了固体放大器在脉冲放大的优势。该技术路线和传统的种子注入技术相比有一定的优势，特别是在严苛的工作条件中，它可以避免复杂的激光腔长主动控制过程，从而使激光系统更加稳定地单频工作。激光脉冲放大过程对信号光的单频特性影响较小，所以只要种子的单频特性足够好，输出放大脉冲的单频特性也将维持足够好。NPRO激光器作为种子激光器，它可以提供稳定的单频种子源，AOM调制获得所需的双脉冲激光脉冲序列，激光脉冲经过三级光纤放大得到3μJ/脉冲，接着又通过双程的Nd:YVO4板条放大器和双程zig-zag Nd:YAG板条放大器，最终输出13mJ/脉冲的双脉冲激光。激光系统的重复频率为30Hz，输出激光的脉宽约为20ns，光束质量因子M2＜1.30，光谱线宽约为34.1MHz。输出的1064nm单频激光可以作为更高能量激光系统的种子激光，同时也可以作为光参量振荡系统的泵浦源，从而获得真正用于探测二氧化碳浓度的1572nm的单频激光。 论文最后对两个方面的研究成果进行了归纳总结，提出了论文研究工作存在的一些不足，并为后续的工作开展提出一些建议。 |
| 英文摘要 | Compact, portable, low-consumption and high-convension-efficency temperature insensitive lasers have important application prospect in the portable laser equipment and lidar systems, especially in eye-safe laser range finder, laser designation and 3D lidar systems. High energy single-frequency double-pulse 1064nm laser could be as pump sources for the optical parametric oscillator (OPO) system and optical parametric amplification (OPA) system to obtain single-frequency double-pulse 1.57μm laser. 1.57μm single-frequency radiation is one of the critical laser sources in an integrated path differential absorption (IPDA) lidar system, which is an efficient method to measure CO2 concentration. The main research works in this article involve temperature insensitive laser technology and high energy single-frequency double-pulse laser source. The research in terms of temperature insensitive laser technology includes theory analysis and experiment exploration. At first, we summarize the development of temperature insensitive laser technology and demonstrate the three basic strategies to realize a stable output laser during wide temperature range: weakening the spectral temperature dependence of pump light, adopting broad-absorped-spectrum gain medium and increasing absorbed path of pump light. The laser is based on the configuration of diode-pump hexagon Nd:YAG slab to realize broad temperature operation. Furthermore, the specific spectrum distribution of LDs which consists of three different wavelength weakens the spectral temperature dependence. According to the result of theoretical simulation, the absorbed efficiency of pump light will maintain more than 93% during -30℃ to 70℃ if the absoubed path in Nd:YAG crystal is more than 46mm and the Nd3+ doping concentration is 1.0 at.%. On the basis of the conclusion of simulation and the principle of geometry, we finish the design of the hexagon slab. A cross-porro prisms polarization-coupled resonator has been implemented in this system, which is insensitive to shock, vibration and large temperature excursion. The research on experiment includes the plane-parallel resonator, the quasi-continuous operation and Q-switch experiments. The Q-switch laser operates during 9℃~45℃ with output energy of approximate112.4mJ, optical-to-optcal efficiency of 13.81% and slope efficiency of 22.66%. The RMS of the output energy is 6.03mJ and the max fluctuation of the output energy is 8.4% within this temperature range. In addition, the pulse width is around 14.3ns and the output spot size is an abuot 5.0x5.0mm square with 3mrad full divergence angle. The beam quality factor of Mx2=19.2, My2=23.9 were recorded. Hybrid maseter oscillator power amplifier (MOPA) modality is an efficient way to obtain high energy single-frequency laser, which combines the advantage of fiber amplifiers with high conversion efficiency and high beam quality and the strenghth of solid-state amplifier in terms of pulse amplification. This scheme can avoid the complex injection-seeding process of actively controlling the cavity length to resonate with the seeder frequency, so it can make the system work steadier. Owing to the fact that the spectrum property is less affected by the process of optical amplification, the single-frequency property of the amplied pulse will maintain excellent if the single-frequency property of the seeder laser is outstanding. The single-frequency seeder laser is a home-made CW nonplanar ring osiclltor (NPRO) Nd:YAG laser at 1064nm. The signal of the double-pulse trains is obtained by an external AOM pulse modulator. Three-stage all-fiber amplifiers are used to obtain pulses with energy of 3μJ per pulse. Then the pulses are amplified by a double-pass Nd:YVO4 slab amplifier and a double-pass Nd:YAG slab amplifier, the energy of pulse is up to 12.7mJ with pulse duration of 20ns. The laser system operate at a reperation rate of 30Hz and the beam qulity factor M2 of output radiation is less than 1.30 with the spectrum linewidth of 34.1MHz. This compact single-frequency double-pulse output MOPA system can be used as a pump source of single-frequency optical prarametric oscillator (OPO) unit for 1572nm emission, or as a qualified seeder for a high energy laser system. Finally, we make a conclusion for the twofold research achievements, present some problems and put forward certain suggestions for the further work. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/17008]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 魏大康. 温度不敏感激光技术及单频双脉冲混合MOPA系统的研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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