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题名	高能钕玻璃双板条热容激光器
作者	孟俊清
学位类别	博士
答辩日期	2005
授予单位	中国科学院上海光学精密机械研究所
导师	胡企铨
关键词	高平均功率 热容 激光器 离轴混合腔
中文摘要	研制近衍射极限的高平均功率固体激光器一直是各国激光工作者追求的一个重要目标。传统的高平均功率固体激光器在工作时对工作介质的冷却使激光工作介质的温度分布不均，从而造成折射率分布不均，并最终严重影响到激光输出的光束质量。因此近几年来国外研究者提出了热容固体激光器的概念，并已经通过建立闪光灯泵浦的片状钱玻璃热容激光器系统证明了这种激光器可以在短时间内得到高光束质量的高平均输出功率，并且计划将建立LD泵浦晶体工作介质的平均输出功率达100kw的热容激光器。而目前国内对这种激光器的研究还处于刚刚起步的阶段，尚未见到相关的实验报导。本文通过对国外相关研究的大量调研，并结合国内过去在高能激光系统方面所做过的研究结果，提出了一种对温度分布不均造成的举光波面实现部分自校正的双板条结构的热容激光器。并且建立了闪光灯泵浦的以两块尺寸为10ox20x50Omm的大尺寸钕玻璃板条为工作介质的激光装置。对介质板条在以两种不同温度的冷却介质同时对两个板条之间和两侧进行冷却的情况下，介质板条的温度分布进行了数值模拟，结果表明该装置以这样的工作方式可以在较高的输入能量下对温度造成的影响进行部分补偿，从而实现较商童复频率的高光束质量输出。同时在调研了目前国内外高功率板条激光器的塞础上，针对这套激光工作系统设计并分析了离轴混合谐振腔的输出特性。该谐振腔腔长为3．2米，大尺寸方向（竖直方向）为离轴非稳腔，其放大倍数M＝1．4份两块腔镜的曲率半径分别为RI＝27．7米和凡＝－21．3米；小尺寸方向（水平方向）为平行平板腔。对远场及近场的光强分布和位相分布分别进行了数值分析，结果表明这种谐振腔较传统的非稳腔不仅可以在远场中心光斑集中更多的激光能量，而且在近场的光场分布为实心方形，从而避免了传统非稳腔在近场输出为中空环形光斑的缺点，因此采用采用这种离轴混合谐振腔将能进一步改善输出光束质量。由于所设计的谐振腔加工周期太长，因此在实验过程中采用三种祸合输出率分别为20％、53％和67％的平行平板腔，对工作在热容状态下的激光输出进行了测试。实验表明，20％的祸合输出率过低，并造成腔内功率密度过高导致增益饱和。采用53％的祸合输出腔片在输入3900焦耳时，得到213．5焦耳的输出能量，并且未见饱和。采用耦合输出率为67％的输出腔片，在输入约20700焦耳l时达到激光闪仇，闪仇输出能址为85焦耳；在输入39000焦耳时得到单脉冲输出能员为370热11，斜率效率1．5％，总体效率为0．94％，通过对近场和5米远处的光斑大小分别进行测量，计算得到竖直方向和水平方向的的发散角分别为lmrad和2mrad。在激光，、作电源充电速度有限的情况下，激光器在热容工作状态下连续输出六个脉冲，利川径向剪切干涉仪对激光输出光束进行观察，干涉条纹结果表明光束质量不会发生大的改变。
英文摘要	It has been long time for researchers developing high average power lasers with diffraction limited output laser beam. In traditional high average power laser systems, cooling the gain media will cause dis-uniform distribution of media temperature, thus cause the dis-uniformity of the refractive index, and reduce the output beam quality seriously. So in recent years foreign researchers proposed the conception of the heat capacity lasers, and proved that this kind of laser can put out high average power laser beam with good beam quality in short times by a flash-pumped Nd glass disk heat capacity laser, further more, they are planning to establish a LD-pumped crystal medium heat capacity laser system as powerful as lOOkW average output power. Up to date, the domestic research in such kind of lasers is only on scratch and have no experimental reort yet... After investigated the relative research abroad and take count of the research of the high energy laser in country, a heat capacity laser configuration of double slabs which can partially correct the distortion of the laser wave front is proposed In this paper, meanwhile, a laser system with double Nd glass slabs is constructed, the dimension of the slabs is 100x20x500mm. The temperature distribution of the medium which are cooled by two different temperature cooling medium between and beside the two slabs respectively is numerically simulated, the results shows that the distortion of wave front can be partially self corrected when the laser is operated in such a working style with high input power, thus the system can operated in high pulse repetition frequency with good beam quality. The output characters of an off-axis hybrid resonator designed for our laser system is analyzed. The total length of the resonator is 3.2 meters, and it's a off-axis unstable resonator in the large dimension (vertical direction) with M=1.4, the radius of the two mirrors is Ri=27.7 and R.2=-21.3 meters, respectively; and it's a F-P resonator in the small dimension (horizontal direction), the numerical analyzing about the distribution of beam intensity and phase in far-field and near-field shows that such a hybrid resonator can not only have more energy in the far-field central lobe than traditional unstable resonators, but also avoid the annular near-field intensity distribution of the traditional resonator and put out a uniformly near-field distribution. It will take a long time to make the hybrid resonator, so we use the F-P resonator with three different output coupling mirrors of T=20%,T=53% and T=67%, and operated the laser system in the capacity mode. The experiment result shows, the output coupling of T=20% is too low and will cause the gain saturation. Using the mirror of T=53%, the output pulse energy will be 213.5 Joule for the 3900 Joule input energy. Using the mirror of T=67%, the threshold of the laser system is about 20700 Joule with 85 Joule output energy. And the output energy will be 370Joule with the input of 3900 Joule, for this time, the system transition efficiency is 0.94%, and the slope efficiency is 1.5%, by measuring the dimension of the output beam at near-field and at 5 meters far away, the divergence is calculated to be lmrad and 2mrad in the two directions, respectively. In the limitation of pumping source, the beam quality of 6 output pulse is tested by the radius direction shearing interferometer , the result shows that working in the heat capacity style, the laser beam quality will not change obviously.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15402]
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	孟俊清. 高能钕玻璃双板条热容激光器[D]. 中国科学院上海光学精密机械研究所. 2005.

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