【作者】 蔡志强；

【导师】 姚建铨；

【作者基本信息】 天津大学 ， 物理电子学， 2004， 硕士

【摘要】 超短脉冲具有皮秒、飞秒量级的脉冲宽度,高脉冲重复频率,宽的光谱和高的峰值功率,在物理、生物学,OCT、激光光谱学、光通信和激光精细加工,非线性频率变换等众多领域具有广泛的用途。自1992年半导体可饱和吸收镜(SESAM)发明以来,由于SESAM激光器所具有的鲁棒性,紧凑性,廉价等优点,使得SESAM在飞秒和皮秒锁模激光器中得到了蓬勃的发展和广泛的应用。国外对SESAM及SESAM锁模激光器的研究已趋成熟,而国内则刚刚起步。在这样的背景下,本文利用国产SESAM,从理论和实验上研究了LD泵浦的Nd:YVO4被动连续锁模皮秒激光器,在17W泵浦功率下,获得了平均功率5.3W的连续锁模脉冲。论文的主要内容可概括为:1、概述了国际上SESAM锁模激光器的几个发展方向,着重介绍了SESAM锁模激光器在各个方向上所取得的最高水平。对大陆的发展情况也作了相应的介绍;2、详细地介绍半导体可饱和吸收镜,涉及SESAM的诞生,SESAM的宏观特性,SESAM的各种类型,三种锁模类型,如何抑制调Q锁模,SESAM的热损伤等;3、对LD端面泵浦激光器,侧面泵浦激光器的热效应进行了研究。利用光线追迹法和有限差分法模拟计算了LD侧面泵浦激光器中,激光棒吸收的泵浦光分布和温度分布,分析了不同的热传导系数对激光棒内温度的影响,后者随前者的增大而减小,且热传导系数有一个最优值;4、利用q参数,首次推导出等效像镜存在第二个解,在使用等效像镜法设计激光谐振腔时,该解在某些情况下更适用。用Visual C++编写了一个谐振腔设计程序,可直观方便地设计激光谐振腔。介绍了两镜直腔,三镜折叠腔,四镜Z型腔的设计方法,对常用的三镜折叠腔提出了改进方法,回顾并介绍了Z型腔的简单设计方法;5、在两镜直腔中,注入泵浦功率为16.42W时,获得了8.32W 1064nm连续输出。对三镜折叠腔,四镜折叠腔,五镜折叠腔锁模激光器进行了实验研究,分析了锁模波形中连续背景的存在原因。最终在五镜折叠腔中,获得了平均功率5.3W的连续锁模输出,注入泵浦功率17W,光-光转换效率31.2%,斜效率34.7%。同时对LD侧面泵浦Nd:YAG锁模激光器做了初步研究。更多还原

【Abstract】 Ultrafast lasers with ultrashort pulse duration, high pulse repetition rate, broadspectrum and high peak intensity are attracting growing interest because of numerousapplications in physics, biology, OCT, laser spectroscopy, high-capacitytelecommunication systems and nonlinear frequency conversion etc. Since theinvention of semiconductor saturable absorber mirrors (SESAM) in 1992, thepassively mode-locked lasers with SESAM have developed rapidly over the pastdecade because of their many virtues such as robust, inexpensive, compact etc. Inforeign countries and Taiwan, many researches have made on the SESAM and theSESAM laser, but there have only a few researches on it in mainland. This thesispresented modeling and experimental results on a LD pumping passivelymode-locked Nd: YVO4 laser with home made SESAM. We obtained continuouswave mode-locked (CWML) pulse trains with 5.3W average output power at theincident pump power of 17W. The main contents can be outlined as follows:1. Summarized several developed directions of mode-locked laser with SESAM ininternational and introduced the highest-level lasers achieved. The status ofmainland has also been introduced.2. Detailed introduced the characteristics of SESAM such as its naissance,macro-parameter, all kinds of structures, three manner of mode locking, how tosuppress the Q-switched mode-locking, thermal induced damage etc.3. Researched the thermal effects of LD end-pumped laser and side-pumped laser.Ray-tracing algorithm and finite difference method are used to simulate theabsorbed power and temperature distributions in crystal rod for differentside-pumping configurations. Simulation results show that there have importanceinfluences on the absorbed power and the temperature distributions at differentpumping configurations and parameters. The relation between the temperature inthe cross-section of the laser rod and the heat transfer coefficient is investigated.The former nonlinearly decreases with the increase of the latter, and thecoefficient has an optimal value.4. To the best of our knowledge, this is first time to deduce the second solution ofequivalent imaging mirror with the method of q parameter. This solution may besuperior to the well-known solution in some conditions. Using the Visual C++, aprogramm for laser cavity design is built. We can easily design a laser cavity by it.Introduced how to design a two-mirror linear cavity, three-mirror fold cavity, andfour-mirror Z-shape cavity. Revised the ordinary three mirror and reviewed asimple design method of Z-shape fold cavity.5. In two-mirror linear cavity, we obtained 8.32W CW output power at the incidentpump power of 16.42W. Experimentally investigated the three-mirror, four-mirrorand five-mirror fold cavity, analyzed the continuous background in mode-lockedpulse trains measured. At last, we obtained CWML pulse with 5.3W averageoutput power in five-mirror fold cavity. The corresponding incident pump powerwas 17W, optic-optic conversion efficiency 31.2% and slope efficiency 34.7%.Then, we preliminarily investigated the LD side-pumping Nd:YAG mode-lockedlaser.更多还原