【作者】 薛迎红；

【导师】 王清月； 柴路；

【作者基本信息】 天津大学 ， 光学工程， 2007， 博士

【摘要】 全固态激光器效率高、体积小、成本低、光束质量好,是当前激光领域的研究热点之一。特别是以掺镱(Yb³⁺)晶体作为增益介质的全固态激光器可以实现高功率、大能量和超短脉冲激光输出,近年来引起了人们的广泛关注。为了开发低阈值、高效率,不同形式激光运转的新型全固态掺Yb³⁺激光器,本论文对国内一些新型掺Yb³⁺晶体开展了系统的激光实验和理论研究,主要包括低阈值的Yb:GSO激光器、高效率的Yb:GdYAB自倍频激光器和自调Q的Yb,Na:CaF2激光器及各种新型激光器的锁模研究。研究结果不仅为新型激光材料的生长和应用提供了参考,而且对发展实用化的新型全固态超短脉冲激光器也具有一定的理论意义和实用价值。论文的主要工作和创新点包括以下几部分:1.利用ABCD传输矩阵对全固态激光器谐振腔内的光斑分布规律进行了分析。根据理论计算,率先在国际上实现了全固态Yb:GSO激光器低阈值激光输出。对利用半导体可饱和吸收镜（SESAM）锁模的谐振腔进行了理论分析,通过选择不同调制深度的SESAM和腔结构分别实现了新型全固态Yb:GSO激光器的调Q锁模和连续锁模脉冲输出。2.首次开展了新型Yb:GdYAB自倍频激光器的实验和理论研究,获得了高达67%的光-光转换效率和宽达67nm的红外激光调谐输出。推导了自倍频激光器动力学方程,分析了决定自倍频功率输出的各种参数,在此基础上进行了全固态Yb:GdYAB激光器的自倍频实验,得到从激光二极管到绿光的转换效率为18.6%,它是迄今为止CW运转的自倍频激光器输出最高的光光转换效率。3.利用SESAM对Yb:GdYAB激光器进行了锁模实验,首次得到了该激光器872fs的超短脉冲输出;并实现了全固态Yb:GdYAB激光器的双波长稳定锁模运转。分析了含自倍频效应的SESAM锁模激光器方程,证明了适度的自倍频效应在锁模激光器中具有抑制调Q和实现稳定锁模的作用。4.系统开展了新型Yb³⁺,Na+:CaF2系列氟化物晶体的激光和荧光实验研究。通过对比实验,证明了掺入Na+具有提高荧光效率,降低激光阈值的作用。利用Yb³⁺,Na+共掺CaF2晶体实现了低阈值激光输出,并发现了Yb,Na:CaF2激光器的自调Q运转特性。通过荧光测量发现,共掺Yb³⁺和Na+的离子浓度有一定配比关系,浓度过高的Na+掺杂反而会降低晶体激光性能,为这种新型晶体的生长和研究提供了依据。更多还原

【Abstract】 The laser diode pumped all-solid-state laser is one of the spotlights in the laser research field, owing to its high efficiency, compact size, low cost and good beam quality. In particular, the all-solid-state laser based on ytterbium-doped gain media has attracted great attention recently because it can generate laser pulses of high power, large energy and ultrashort duration. In order to search for new all-solid-state lasers with low threshold, high efficiency, systematic experimental and theoretical laser studies have been carried out in this dissertation on various types of novel laser crystals including low threshold Yb:GSO lasers, high efficiency self-frequency-doubling （SFD） Yb:GdYAB lasers, self-Q-switched Yb,Na:CaF2 lasers, and their mode-locking studies. The studies provide guidance for new laser crystal growing, and are of theoretical and practical value for the development of a new generation of all-solid-state ultrafast lasers. In this dissertation, my work and innovations will be presented as follows:1. The rule that governs the intra-cavity laser spot distribution of LD pumped lasers is analyzed using ABCD transmission matrix. Based on that rule, a low threshold LD pumped Yb:GSO laser is developed for the first time to our knowledge. The theory of SESAM-based mode-locking lasers is analyzed, and both Q-switched and CW mode locking operations of all-solid-state Yb:GSO lasers are obtained using different cavity configurations and SESAMs with different modulation depths.2. Experimental and theoretical studies on SFD Yb:GdYAB lasers have been performed for the first time. An optical conversion efficiency of 67% and an infrared tunable spectrum of 67 nm are achieved, respectively. The critical parameters that determine SFD efficiency are analyzed in detail through the dynamic equation derived for SFD lasers. Based on the theoretical analysis, a conversion efficiency of 18.6% from LD to green light is achieved, which is the highest optical conversion efficiency from LD to SFD visible up to now.3. A SESAM mode locking Yb:GdYAB laser is built, with an ultrafast laser pulse output of 872 fs. Stable two wavelength （infrared and visible） operation of the mode-locked solid state Yb:GdYAB laser is also achieved for the first time. The dynamic equation for SESAM mode-locked lasers including SFD is derived. It is proved that appropriate self second harmonic generation in mode-locked lasers can suppress the tendency of Q-switched operation. 4. Laser and fluorescence experiments are carried out on a series of novel Yb,Na:CaF2 crystals. According to comparative experiments, it is proved that Na+ dopants can increase the fluorescence efficiency and lower the lasing threshold. A low threshold laser is realized in Yb³⁺, Na+ co-doped CaF2 crystals. Self-Q-switched mode-locking operation of the Yb,Na:CaF2 laser is observed. An appropriate co-doping concentration of Yb³⁺ ions and Na+ ions is found according to measured fluorescence, providing guidance for new laser crystal growing and research.更多还原