【作者】 张三军；

【导师】 曾和平；

【作者基本信息】 华东师范大学 ， 光学， 2004， 硕士

【摘要】 脉冲激光器在激光雷达、通讯、材料加工、非线性频率转换等领域具有广泛的应用，采用半导体激光器泵浦的固体激光器具有转换效率高、工作寿命长、结构简单、性能稳定等诸多优点，所以在半导体激光器泵浦的固体激光器中通过调Q或者锁模的方法实现短脉冲激光输出已经成为激光器发展的新方向。在本论文中，我们讨论了在半导体激光器泵浦的Nd：GdVO₄固体激光器中获得调Q锁模（和连续锁模）脉冲激光输出的几种方法。 作为一种新的激光品体，Nd：GdVO₄具有导热性能好、吸收截面大、发射带宽宽等优点，因此决定了它在同类激光晶体中具有很强的竞争力。在第一章中，我们简述了调Q锁模的理论，介绍了Nd：GdVO₄晶体的特性并且与几种常用的晶体进行了比较。然后在后面的三章中，我们分别讨论了三种在Nd：GdVO₄固体激光器中获得调Q锁模脉冲方法，如下所述： 用可饱和吸收体Cr⁴⁺：YAG实现调Q锁模：因为Cr⁴⁺：YAG的具有基态饱和吸收（GSA）和激发态饱和吸收（ESA）特性，并且其相应能级的弛豫时间分别在微秒和皮秒量级，我们可以利用Cr⁴⁺：YAG的这种特性来构建凋Q锁模的激光器。实验中我们获得了波长在1.06μm、最大输出功率为3.22 W的调Q锁模激光脉冲输出，并且对调Q锁模的调制深度以及其转变为连续锁模可能性进行了讨论。 用半导体可饱和吸收镜（SESAM）调Q锁模：SESAM具有两种不同的时间响应特性，这使得在用SESAM实现锁模的时候也会产生调Q的脉冲包络，可以用SESAM的这种特性来构建调Q锁模的激光器。实验中我们在获得了1.06μm的最大输出功率为3.5W的调Q锁模激光脉冲输出和最大输出功率4.9 W的连续锁模脉冲输出。通过自相关测量测得连续锁模脉冲的宽度为11.5 ps。在这部分内容里，我们同样对调Q锁模到连续锁模的变化条件进行了讨论。 N矿＼GdVO。晶体的自锁模：我们简单分析了获得自锁模的方法，并且通过实验在＊矿＼0dVO。激光器中获得自锁模脉冲输出。但足山／＊矿‘离于的上能级比较长，在产生自锁模的同时比较容易产生闩⑤Q，实验小我们获得了自调Q自锁模的激光脉冲。我们讨论了抑制自调Q包给的方法，并且在实验中获得了稳定的连续自锁模脉冲。更多还原

【Abstract】 Pulsed lasers have been used widely in various fields, such as range finder, optical communication, material process, and nonlinear frequency conversion. Diode-pumped solid-state lasers have various advantages such as high conversion efficiency, long working lifetime, simplicity, and stability. Consequently, developing techniques for Q-switching or mode-locking in diode-pumped lasers has been burgeoning as new exploration to get compact pulsed lasers. In this dissertation, we discuss several techniques to generate Q-switched mode-locked (or stable cw mode-locked) laser pulses in diode-pumped Nd:GdVO4 solid-state lasers.In chapter 1, we firstly review the history of diode-pumped solid-state lasers and give a brief introduction to the theory of Q-switched mode-locking. Secondly, we present the properties of Nd:GdVO4 crystal and compare it with several commonly used laser crystals. As a new laser material, Nd:GdVO4 crystal has the advantages of high thermal conductivity, large absorption cross-section and wide emission bandwidth and so on, which make the Nd:GdVO4 crystal more competent than some other laser crystals. And in the following three chapters, we demonstrate three techniques to obtain Q-switched mode-locked (or cw mode-locked) lasers pulses in diode-pumped Nd:GdVO4 solid-state lasers.Q-switched mode-locking with Cr4+: YAG crystals: Cr4+:YAG possesses the properties of ground-state saturable absorption (GSA) and exited-state saturable absorption (ESA). And the relaxation times of GSA and ESA are in the region of microsecond and picosecond, respectively. Those characteristics can be applied to construct Q-switched and mode-locked lasers. In our experiments, we obtained 3.22 W Q-switched and mode-locked laser output in the 1.06 μm. The modulation depth and the probability of obtaining cw mode-locking are also discussed in this part.Q-switched mode-locking with semiconductor saturable absorber mirrors (SESAMs): SESAMs have two kinds of response times, which usually lead to the Q-switched pulse envelope in the lasers mode-locked by SESAM. Therefore, SESAM can be used to achieve Q-switched mode-locked laser pulses. In the experiments, we obtained 3.5 W Q-switched mode-locked and 4.9 W cw mode-locked laser outputs. The pulse width of the cw mode-locked pulse was measured by a homemade autocorrelator to be 11.5 ps. The condition of transforming from the Q-switched mode-locked to cw mode-locked operation was also discussed in this part.Self-mode-locking in Nd3+:GdVO4 lasers: we analyzed simply the method to achieve self-mode-locking, and experimentally obtained self-mode-locked pulse train in the Nd3+:GdVO4 laser. Due to the long upper-level life-time of Nd3+ ions, the self-mode-locked pulses tend to concentrated in the self-Q-switched envelope. Therefore, in our experiment, self-Q-switched self-mode-locked laser pulses were achieved. In this part, we discussed methods to suppress the self-Q-switched envelopes and experimentally obtained stable cw self-mode-locked laser pulses.更多还原