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题名	多光束激光光源的研究
作者	于真真
学位类别	硕士
答辩日期	2013
授予单位	中国科学院上海光学精密机械研究所
导师	侯霞
关键词	多光束 激光雷达 多程放大 微型激光器
其他题名	Research on Multi-beam Laser System
中文摘要	随着激光技术尤其是多元阵列探测技术的发展，基于阵列激光并行发射和接收的多光束推帚式激光雷达探测技术正成为国内外研究的热点。相较于单光束探测，多光束的推帚式探测可实现高精度、垂直分辨、宽幅宽等，应用前景十分广阔。作为其关键技术之一的多光束并行发射激光光源需要具有高效、体积小、质量轻、工作稳定等特点。 本论文基于推帚式激光雷达对多路激光光源的需求，对多路激光光源技术进行研究，以得到高光束质量、高单脉冲能量的阵列激光光源。论文研究内容主要包含以下几个方面： 1）对激光高度计的工作原理及其不同探测方式对光源的要求进行阐述，并介绍多光束星载激光雷达的探测原理，对多光束激光雷达探测技术的发展现状及多光束激光光源技术进行调研，提出本论文中的多光束激光光源的方案：一是对多路固体激光器或者光纤激光器的输出同时进行直通放大，研究多路激光放大的可行性。二是研究小型、高效的激光系统，在对激光光束元数要求不高的情况下，小型激光器阵列不失为多光束光源的一种选择。 2）设计研制LD侧边抽运的Nd:YAG板条放大模块，对板条直通多程放大技术进行研究。首先针对单束光进行多程放大，理论模拟并分析了放大器的储能及性能，然后对整个激光振荡-放大系统进行实验研究。结果表明，LD双侧边抽运时，部分没有被吸收的抽运光透过板条对异侧 LD的出光造成一定影响，使得放大器增益较低。采用单侧抽运时，由于增益分布不均匀，放大后光斑变差，具有两个光强中心。 3）在小型、高效的激光器的研究方面，分别针对VCSEL端面抽运的种子源和尾纤LD端面抽运的种子源的信号光，利用LD侧边抽运的Nd:YAG板条晶体对掠入射式多程放大技术进行研究。掠入射的信号光在抽运面进行全反射放大，可充分利用晶体增益强区。对于VCSEL抽运的种子源的放大，放大器双程增益为11，并且放大后光源保持较好的光束质量，能量提取效率为19.46%。对于LD端面抽运的种子源的放大，四程放大后的单脉冲能量约为1.1mJ。放大器有效提取效率约为25.0%，光-光转换效率约为3.6%。整个振荡-放大系统结构紧凑、简单、体积小巧，且具有高重复频率工作的潜力，可用来构成激光器阵列。 4）相对于侧边抽运，端面抽运方式可以实现信号光与抽运光较好的模式匹配，故论文最后对LD端面抽运的Nd:YAG板条晶体的双程放大器进行了初步研究。建立理论模型分析放大器大的性能，设计了激光振荡放大系统，为进一步的实验研究做好准备。 经过以上实验验证，由VCSEL端面抽运或者尾纤抽运的Nd:YAG激光振荡级和LD侧边抽运的掠入射式Nd:YAG板条多程放大级组成的激光振荡-放大系统，进一步优化后，可以作为激光器阵列，为所需的阵列激光光源提供参考。
英文摘要	As laser techniques, especially the multi-element array detecting technology, advances, a non-scanning multi-beam, swath-mapping lidar, which is based on multiple laser transmitting beams and detector array receiving, is becoming a research hotspot. Compared with measurements by a single beam, the pushbroom approach enables high-accuracy, vertical resolving, wide swath mapping and so forth, thus having bright prospect. Multi-beam laser transmitting systems, as one of the key technologies, should be high-efficiency, compactness, low weight, reliability and robustness. Based on the need for multiple laser beams of push-broom lidar, the multi-beam laser technology is studied to achieve high beam quality and high energy pulses. Several main aspects are listed as follows: 1) The principle of lidar altimeter and requirements of laser using different detecting methods are introduced. The operating mechanism of spaceborne multi-beam lidar and its progress are presented. Under the investigation of the multi-beam laser technology, two approaches to obtain multiple beam laser transmitting are proposed. The first is a straight multi-pass slab amplifier for simultaneous amplification of laser beam array from solid-state lasers or fiber lasers. The other is the study of compact, high-efficiency lasers aiming at using lasers array to achieve multiple beams. 2) As for the first method, a LD bars side-pumped Nd:YAG slab amplifier, based on theoretical analysis, is designed, and the straight multi-pass amplification of a single laser beam is investigated. Experimental results show that the unabsorbed pumping light from one side has negative effect on the operation of LD bars on the other side when double-side pumping is adopted, thus lowering the gain of the amplifier. On the other hand, with single-side pumping, the absorbed pumping light is non-uniformly distributed, which results in there being two stronger centers in the amplified laser spot. 3) About the study of compact and high-efficiency lasers, the amplification of VCSEL end-pumped and fiber-coupled LD end-pumped seeders are discussed respectively. A diode-pumped, multi-pass and grazing incidence Nd:YAG slab amplifier is developed. The laser beam experiences total internal reflection and amplification on the pumped side to use the region of the highest gain. For the amplification of VCSEL pumped seeder, the good beam quality of the seeder is preserved. The gain of double pass amplification and efficiency of absorbed energy extraction are 11 and 19.46% respectively, which is in accord with theoretical analysis. For the four-pass amplification of LD pumped seeder, ~1.1 mJ pulse energy, ~25% effective extraction efficiency and 3.6% optical-to-optical efficiency are obtained. Both of the two oscillator-amplifier systems are compact, simple, small size and able to operate at high repetition rate. By optimizing the efficiency and size of the systems, they can be used to form lasers array, which could be a building block for future airborne or spaceborne lidar remote sensing applications. 4) Compared with side-pumping, the end-pumping can provide excellent overlap of laser with pumping light. Therefore, some primary studies are conducted on a fiber-coupled LD end-pumped, double-pass Nd:YAG slab amplifier. A theoretical model is made to analyze the amplifier performance, then an oscillator-amplifier is designed. Limited by experimental conditions, such as suitable pumping LD, driving power, the further study is to be continued. With the results obtained from above experiments, our approach to achieve a multi-beam laser source is using the array of compact, simple oscillator-amplifiers, which consist of a diode-pumped, multi-pass and grazing incidence Nd:YAG slab as the amplifier seeded by a VCSEL or fiber-coupled LD end-pumped oscillator. The laser may form the basis for our future work on laser beam array.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16744]
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	于真真. 多光束激光光源的研究[D]. 中国科学院上海光学精密机械研究所. 2013.

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