QQ客服 官方微博 反馈留言

题名	掺Yb~(3+)激光晶体的生长、缺陷、光谱及激光性能的研究
作者	杨培志
学位类别	博士
答辩日期	1999
授予单位	中国科学院上海光学精密机械研究所
导师	邓佩珍
关键词	晶体生长 缺陷 光谱特性 激光性能
中文摘要	高强的窄带泵浦源InGaAs二极管的出现和人们对LD泵浦的固体激光器的高效、高功率、小型化和集成化的追求，唤起了人们参掺Yb~(3+)激光材料的研究兴趣。尤其是随着激光二极管作为惯性约束核聚变择优泵浦源的出现和掺Yb~(3+)激光材料在通信、军事上巨大的应用潜力，更将掺Yb~(3+)激光材料的研究推向了高潮。在目前研究的掺Yb~(3+)激光晶体中，Yb:YAG晶体由于具有良好的光谱特性、优异的光学、热力学和机械性能而成为掺Yb~(3+)激光晶体中的佼佼者；碳灰石结构晶体(如Yb:FAP)由于能给Yb~(3+)离子提供其它基质无可比拟的晶场环境而使其具有优异的光谱特性，因此，受到人们的青睐。基于此，本文全面系统地研究了Yb:YAG晶体和Yb:FAP晶体。本论文的主要工作和创新点摘要如下：1. 用引上法成功地生长了四种掺杂浓度的Yb:YAG晶体，晶体的毛坯尺寸为φ31～33 * 90～110mm，掺杂浓度分别为5at.%，1010at.%，20at.%和30at.%。获得了理想的生长工艺参数。为消除晶体中的应力和色心，研究了晶体的退火工艺，并获得了理想的退火工艺参数。对Yb~(3+)在晶体中的分布进行了分析。结果表明：Yb~(3+)在Yb:YAG晶体中的纵向和径向浓度分布均匀。2. 首次成功地生长了Yb~(3+)掺杂浓度高达30at.%的Yb:YAG晶体，通过合适的退火工艺后，获得了低散射损耗、无色心和低位错密度的高质量单晶。3. 用引上法生长了Yb~(3+)掺杂浓度为0.5at.%～5at.%的Yb:FAP晶体，晶体的毛坯尺寸为φ15～22 * 20～60mm，为消除晶体中存在的宏观缺陷，研究了晶体中的组分配比和退火工艺条件，获得了较理想的组分配比和原位退火工艺参数。为今后生长高质量的Yb:FAP晶体奠定了基础。4. 用化学腐蚀法研究了Yb:YAG晶体和Yb:FAP晶体的位借，估算了Yb:YAG晶体和Yb:FAP晶体中的位错密度。结果表明：Yb:YAG晶体的位错密度较低，均小于10~2cm~(-2)，近乎为无位错晶体，因此，生长的Yb:YAG晶体具有高度的晶格完整性。Yb:FAP晶体(101-bar0)面的位错密度约为10~4～10~6cm~(-2)。获得了两类晶体的几个低指数面的位错蚀坑形状。5. 用同步辐射X射线形貌照相研究了Yb:YAG晶体和Yb:FAP晶体中的缺陷及其分布。在Yb:YAG晶体中，位错主要来源于籽晶以及晶种和生长界面处位错成核，通过优化生长工艺可以消除位错；在沿[1-bar21-bar0]方向生长的Yb:FAP晶体中观察到平行于(0001)面的小晶界，晶体的下部由于组分的挥发出现严重的组分偏析、气泡和包裹物。6. 研究了Yb:YAG晶体在300nm～800nm的吸收特征，指出晶体中373nm的吸收带是由于Yb~(2+)所致，630nm左右的吸收带则是由Yb~(2+)微扰下的Re-F色心所致。这两个吸收带的存在会减弱晶体的本征吸收和本征发射强度，对荧光寿命具有严重的猝灭作用。7. 通过吸收光谱、发射光谱和荧光寿命的测量研究了Yb:YAG晶体和Yb:FAP晶体的光谱特性。用倒易法计算了晶体的发射截面。结果表明：Yb:YAG晶体具有三个吸收峰、大的吸收系数、宽的吸收带和发射带以及长的荧光寿命，适于LD泵浦的高功率固体激光器，燕可在一定波长范围内调谐；1.03μm波长处宽的发射线宽使其能实现超短脉冲激光输出。大的吸收系数有利于实现微片固体激光器。而Yb:FAP晶体具有大的吸收截面和发射截面，吸收线宽和发射线宽均较窄，适于LD泵浦的中、低功率的固体激光器。8. 首次研究了紫外光子激发和X射线激发Yb:YAG晶体的荧光光谱特征。9. 根据Yb:YAG晶体的光谱特性，设计了用InGaAs LD泵浦Yb:YAG晶体微片的激光实验装置。用940nm的InGaAs LD泵浦20at.% Yb:YAG晶体微片获得了300mW 1.03μm的激光输出，斜率效率为30%，外推阈值功率为188mW；10. 用钛宝石激光器泵浦不同掺杂浓度的Yb:YAG晶体微片，均获得了波长为1.053μm激光输出。当输出耦合镜的T_(1.053μm) = 4.26%时，掺杂浓度为10at.%、厚度为1mm的Yb:YAG晶体微片的最大激光输出功率为320mW，斜率效率为54%，外推阈值功率为203mW；掺杂浓度为20at.%、厚度为0.5mm的Yb:YAG晶体微片的最大激光输出功率为356mW，斜率效率高达69%，外推阈值功率为273mW。当泵浦功率远高于阈值时，斜率效率达72%。这是迄今报道的1.053μm波长处激光输出的最高斜率效率。
英文摘要	The heart of solid-state laser lies the gain media, which have profound impacts on laser operational parameters such as wavelength, power, Q-switching, mode-locking, and beam quality. The advent of intense, narrow-band optical pump source -InGaAs LD and the demands for laser diode pumped solid-state lasers toward high efficiency, high-power, compact and miniature have stimulated the interests in Yb-doped laser materials. Especially, the emergence of laser diodes as the preferred pump source for inertial confinement fusion (ICF) and Yb-doped materials presented enormous potential for communication and military applications give impetus to the study of Yb-doped materials. Among the numerous Yb-doped crystals, Yb:YAG and Yb-doped apatite series possess excellent spectra and laser performance. CW, pulse and femtosecond laser operation have been achieved in LD pumped Yb:YAG and Yb:FAP crystals. So, it is necessary to investigate Yb:YAG and Yb:FAP systematically and deeply. The main results in this work were summed up as follows: (1) Yb:YAG with different Yb~(3+) doping concentrations were successfully grown by the Czochralski method. In order to minimize strains and eliminate color center in Yb:YAG, the annealed condition were studied and optimal parameters were found. The distribution of Yb~(3+) in Yb:YAG which was determined by absorption spectra was uniform. (2) High-quality Yb:YAG with Yb~(3+) doping level up to 30at.% was first grown by the Czochralski method. (3) Yb:FAP with Yb~(3+) doping concentrations of 0.5～5at.% were grown by Czochraski method. In order to eliminate the common imperfection visible in Yb:FAP, the different stoichiometric compositions in Yb:FAP and the annealed conditions were studied. The relatively ideal stoichiometric composition in Yb:FAP and annealed conditions were acquired. (4) Dislocation etching pits on three low index faces of Yb:YAG and on two low index faces of Yb:FAP were revealed by chemical etching method. The dislocation densities of Yb:YAG and Yb:FAP measured were lower than 10~2 cm~(-2) and 10~4～10~6 cm~(-2) respectively. (5) By means of synchrotron radiation X-ray topography, we found that the grown-in dislocations in Yb:YAG mainly originate from two sources: (a) continuation of those which were already present in the seed; (b) nucleation at the seed-crystal interface. Low-angle boundaries parallel to the (0001) plane were observed in Yb:FAP grown along [1-bar21-bar0], and precipitations, bubble and inclusions were also observed in Yb:FAP. (6) The absorption spectrum of Yb:YAG at 300nm～800nm were studied and two absorption bands were observed. One absorption band centered at 373nm is attributed to Yb~(2+) and another absorption band centered at 670nm is associated with Re-F color center perturbed by Yb~(2+). These two absorption bands weaken the intrinsic absorption intensity and intrinsic emission intensity of Yb:YAG, and lead to the fluorescence quenching. (7) The fluorescence spectra of Yb:YAG excited by X-ray and by UV lamp at 240nm was first studied in this work. (8) The spectroscopic properties of Yb:YAG and Yb:FAP were assessed by measuring absorption spectra, emission spectra and fluorescence lifetimes. The emission cross sections have been evaluated using absorption cross section and the principle of reciprocity. The results have shown that Yb:YAG has enormous potential for laser diode pumped solid state lasers with high power and high efficiency. Yb:FAP should suit for many diode-pumped solid state laser application to low- and medium-power. (9) A room-temperature 20at.% Yb:YAG thin chip laser operating at 1.03μm pumped by an InGaAs diode laser operating at 940nm has been realized. The extrapolate threshold was 188mW, and pulsed laser output power of 300mW was obtained for a pump power of 1.2W. The slope efficiency was 30%. (10) Efficient room-temperature Yb:YAG thin chip lasers operating at 1.053μm pumped by Ti:Sapphire laser operating at 940nm have been developed. For 10at.% Yb:YAG, The CW output power of 320mW was obtained with an absorbed pump power of 791mW, the slope efficiency was 54%; And for 20at.% Yb:YAG, CW output power of 356mW was obtained with an absorbed pump power of 784mW, slope efficiency was 69%. Slope efficiency was as high as 72% with absorbed pump power exceeding 730mW. To our knowledge, this is the highest slope efficiency of Yb:YAG laser at 1.053μm up to date.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15317]
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	杨培志. 掺Yb~(3+)激光晶体的生长、缺陷、光谱及激光性能的研究[D]. 中国科学院上海光学精密机械研究所. 1999.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。