【作者】 张玉萍；

【导师】 姚建铨；

【作者基本信息】 天津大学 ， 物理电子学， 2007， 博士

【摘要】 全固态激光器(半导体泵浦的固体激光器)具有体积小、重量轻、效率高、光束质量好、稳定性好,维护费用低等优点,随着激光技术的发展,其在工业、军事、医疗和科研等领域中发挥着越来越重要的作用,已成为应用激光器中的主流。高功率全固态绿光激光器因其在激光材料加工、激光彩色显示、激光医疗以及激光同位素分离等领域的重要应用而成为研究的热点。本文的研究工作主要集中在高功率全固态1342nm激光器、1064nm激光器、准连续和连续全固态绿光激光器的理论和实验研究等方面。本文的主要创新点可以归纳如下:1.研究了1342nm二极管激光器单端泵浦Nd:YVO4激光器,在实验中采用弱聚焦耦合系统、使用低掺杂浓度晶体以及合理的腔型设计获得了7.36W稳定的TEM00模1342nm激光输出,光-光转换效率32.8%,功率不稳定度0.3%。此结果在1342nm激光器的功率稳定性方面处于国际领先水平,在端面泵浦1342 nm Nd:YVO4激光器功率水平方面为国内最高。2.从理论上研究了双棒之间距离对稳定性和光束质量的影响,结果显示,在热致双折射补偿腔中,当双棒分别靠近激光器腔镜时可以得到更低的M2值,同时发现,双棒内主平面之间距离应接近热焦距长度之和,这样在补偿热致双折射的同时可以实现高功率无损伤运转。然而,在含90°旋光片的对称平行平面双棒谐振腔中,热致双折射补偿造成法向(fr)和切向(fφ)热焦距长度的轻微不对称,打破了谐振腔的对称性,在稳区中产生一个窄的非稳区。由于这个窄非稳区的存在,当泵浦激光功率上升到此处时激光输出功率会出现波动或下降。因此,有必要消除这个窄的非稳区以得到激光功率随泵浦电功率的稳定线性增长。通过g参数分析,我们发现对称共焦腔结构方法,可以消除稳区中存在的非稳区,我们也研究了该腔结构下双棒之间距离对稳定性和光束质量的影响。3.用传输矩阵法,通过稳区图分析了单棒对称和非对称平行平面腔结构。在分析稳定条件、r偏振和φ偏振模式尺寸的基础上,阐明了不同谐振腔内实现激光稳定运转的条件。又从理论上分析了有热致双折射补偿和无热致双折射补偿双棒串接腔中,r偏振和φ偏振对谐振腔稳定条件的影响,得到了短腔和长腔情况下的稳区最大范围。并从实验上进行了验证,理论与实验相一致。在双棒短腔情况下,获得了482.3W的1064nm激光输出功率,光-光转换效率40.2%。4.通过对介质中耦合波方程的求解,对不同情况下Q开关的衍射效率进行分析,并介绍了几种新型声光Q开关的工作原理。用龙格-库塔法数值求解内腔倍频激光器的声光调Q速率方程,得到内腔倍频激光器中倍频晶体的最佳长度以及倍频晶体最佳长度与泵浦水平和腔内损耗的关系。为声光调Q绿光激光器的研究奠定了基础。5.分别采用50W和150W半导体侧泵模块、进行了单棒和双棒串接声光调Q内腔倍频绿光激光器的研究。用一个50W模块得到31.2W 532nm绿光输出,重复频率7kHz,光-光转换效率17.3%,功率不稳定度小于1%。用两个50W模块双棒串接,得到56W 532nm准连续绿光输出,重复频率9kHz光-光转换效率15.6%,功率不稳定度小于1%。采用单个150W模块进行绿光实验,用KTP内腔倍频得到68.3W的绿光输出;用LBO内腔倍频得到66.6W的绿光输出,后者光-光转换效率18.2%。已经开发出20W和40W绿光激光器产品,整体性能处于国内领先水平。6.进行了高功率连续绿光激光器的实验研究。采用侧面泵浦方式和三镜折叠谐振腔设计,高效KTP晶体作为腔内倍频晶体,用北京国科和武汉三浦的泵浦组件,分别得到20.7和22.7W的连续波绿光激光输出,功率不稳定度在1%左右,能够很好的满足激光彩色显示等领域对高功率连续绿光的要求。据我们所知,此结果在532nm连续绿光输出功率水平方面为国内最高,在采用棒状工作物质的全固态连续绿光激光器中,其输出功率达到国际先进水平。更多还原

【Abstract】 All-solid-state lasers (Laser diode-pumped solid-state lasers) have many advantages, such as compact, efficient, good beam quality, stable and long lifetime et al. With the development of laser technology, they have been widely used in the fields of industry, military, medical treatment and research, and have become the mainstream of lasers in application. High-power LD pumped green laser has become the research focus because its important application in material processing, medical application and laser isolation of uranium isotopes, etc. This doctoral dissertation focuses on theoretical and experimental research of high-power all-solid-state 1342nm, 1064nm, quasi-continuum and continuum 532nm lasers.The main contents and key creation points of this dissertation are as follows:(1) A compact, efficient and high-power diode-laser single-end-pumped Nd:YVO4 laser with continuous-wave emission at 1342nm is investigated. A coupling system with a large working spot size of 800μm, a low-doping Nd:YVO4 crystal and reasonable designed resonator are used in the experiments. And we obtained an output power of 7.36W, corresponding to an optical-to-optical efficiency of 32.8%. The laser operates in a nearly TEM00 mode with small amplitude noise of 0.3%(rms). This represents, to the best of our knowledge, the highest power obtained from a diode-laser single-end-pumped Nd:YVO4 continuous wave laser at 1342nm so far and the power stability keep ahead in the world.(2) We investigate the effect of distance between two rods of a double laser-head plane-parallel resonator on stability and beam quality. The results show that, in a thermal-birefringence compensation scheme, low M2 value can be achieved when each rod is, respectively, placed near each laser mirror. And we find that the distance between two inner principal planes of two rods should be near the sum of the thermal focal lengths to compensate a thermal birefringence as well as to get high power without optical damage. In symmetrical plane-parallel two-rod resonator with 90°optical rotator, the thermal birefringence compensation breaks the symmetry of the resonator configuration, which is due to the slight difference between the thermal focal lengths of the radial (fr) and the tangential (fφ) directions of a laser rod. This generates a narrow unstable region inside a stable region, which means a laser power drop in the unstable region as increasing the electric pump power. We propose a method to eliminate the narrow unstable region of a symmetric two-rod resonator with a 90°optical rotator which is used to compensate for thermal birefringence of the laser rod. Using the g-diagram analysis, we find that the narrow unstable region can be removed in the resonator configuration of a symmetric confocal type. We investigate the effect of the distance between two rods of the proposed resonator on the stability and the beam quality.(3) Using a ray matrix method, the resonator stability conditions are analyzed graphically in the symmetric and asymmetric configuration for a plane-parallel resonator. On the basis of an analysis of the stability condition and mode size for the r andφpolarization, we clarify how the stable laser operation is possible for various resonator configurations. Experimentally, the output power characteristics are confirmed in association with the resonator stability. We also analyze theoretically how the r andφpolarization affect the resonator stability condition of two laser heads with or without thermal birefringence compensation. The resonator stability condition is analyzed graphically for a plane-parallel resonator. The maximum range of stable region is found for both the short and the long cavity. The characteristics of the laser output power are confirmed experimentally in association with the resonator stability condition. The laser output power of 482.3W is obtained with the optical-to-optical efficiency of 40.2% for a plane-parallel resonator with a short crystal separation.(4) We analyzed the diffraction efficiency of Acousto-Optic Q-switch (A-O Q-switch) in different cases by solving the coupled wave equation in the medium. And we introduced working principles of several new types of A-O Q-switches. We solved the A-O Q-switched laser rate equations of intracavity frequency-doubled lasers with Runge-Kutta method, obtained optimum length of frequency-doubled crystal, the relation between the optimum length of frequency-doubled crystal and the pump level, the cavity loss. This is the basic of the high power A-O Q-switched green laser.(5) Use 50W, 150W side-pumped laser modules, we investigated single-rod and double-rod A-O Q-switched intracavity-doubled lasers. Using a 50W module, we obtained a green average power of 31.2W with 7 kHz repetition, with optical-to-optical conversion efficiency of 17.3% and power instability of less than 1%. With two 50W modules in tandem with each other, we obtained an average power of 56W at 532nm with 9 kHz repetition, of which the optical-to-optical conversion efficiency is 15.6%, and the power instability is less than 1%. Using the 150W pump module with KTP crystal, we obtained 68.3W green output power. Using the same module with LBO crystal, we obtained 66.6W green output power with optical-optical conversion efficiency of 18.2%. The experiments have been developed into products of 20W and 40W green lasers, the whole performance keep ahead in our country.(6) Research on high power continuum wave (CW) green laser. With an LD side-pumped configuration and three mirror folded cavity design, we obtained 20.7W and 22.7W CW 532nm output power with the pump modules from Beijing GK Laser Technology Co. Ltd. and Wuhan Sapo Laser Industry LTD., respectively. The power instability is about 1%. This can satisfy the demand of CW green laser in laser color display field. This represents, as far as we know, the highest power of CW 532nm output power in our country. And in traditional laser with rod material, this output power is advanced in the world.更多还原