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1、硕士学位论文半导体端面泵浦高重频电光调 Q Nd:GdVO4 激光器的研究RESEARCH ON LASER-DIODE END-PUMPING HIGH REPETITION RATE ELECTRO-OPTICAL Q-SWITCHED Nd:GdVO4 LASER王成哈尔滨工业大学2011 年 6 月国内图书分类号：TN248.11 学校代码：10213国际图书分类号：535-15 密级：公开 工学硕士学位论文半导体端面泵浦高重频电光调 Q Nd:GdVO4 激光器的研究硕士研究生 ： 王成导 师 ： 于欣教授申请学位 ： 工学硕士学科 ： 物理电子学所 在 单 位 ： 航天学院答 辩
2、日 期 ： 2011 年 6 月授予学位单位 ： 哈尔滨工业大学Classified Index: TN248.11 U.D.C: 535-15 Dissertation for the Masters Degree in EngineeringRESEARCH ON LASER-DIODE END-PUMPING HIGH REPETITION RATE ELECTRO-OPTICAL Q-SWITCHED Nd:GdVO4 LASERCandidate： WANG ChengSupervisor： Prof. YU XinAcademic Degree Applied for： Maste
3、r of EngineeringSpeciality： Physical ElectronicsAffiliation： School of Astronautics Date of Defence： June, 2011Degree-Conferring-Institution： Harbin Institute of Technology哈尔滨工业大学工学硕士学位论文- I -摘 要半导体端面泵浦全固态激光器（DPSSL）具有效率高、光束质量好、结构紧凑等优点，已成为当今激光器领域研究的热点。调Q 技术是获得脉冲激光输出的关键技术，并广泛应用于微机械加工、激光通信、激光雷达等众多工业军事领
4、域。与其他调Q技术相比，电光调Q技术具有开关速度快、关通能力强、稳定性高的优势，易于获得高重复频率、窄脉宽、高峰值功率的脉冲激光输出。Nd:GdVO 4晶体具有大的吸收截面和大的发射截面、适中荧光寿命、高的热导率以及偏振发射等特性，使其成为理想的高重频运转激光介质。鉴于此，本文致力于研究半导体端面泵浦高重频电光调Q Nd:GdVO4激光的特性，包括脉冲反射式调Q特性以及脉冲透射式调Q（腔倒空）特性等。本文首先分析了影响激光器输出功率、效率和光束质量的重要因素模式匹配问题和热效应问题。根据连续激光输出功率与模式匹配的关系，推导了不同泵浦功率下振荡光斑尺寸与泵浦光斑尺寸的最佳比值。在分析激光器产热
5、机制的基础上，探讨了激光器的热透镜效应，并分析了激光器的热致衍射损耗效应与泵浦功率和腔模尺寸的关系。最后研究了控制与补偿热效应的措施，并模拟了其减小热效应影响的效果。从连续泵浦固体激光器的速率方程出发，推导了调Q 激光重要参数如脉冲宽度、脉冲能量、峰值功率等与泵浦功率和运转重频的关系，并且得到了最佳输出镜反射率与增益和损耗的关系。根据理论指导，通过实验实现了电光调Q 1063 nm Nd:GdVO4脉冲激光输出。激光最高运转重频为 100 kHz，峰值功率为2.6 kW，对应脉宽为20.6ns。同时通过与声光调Q激光器的对比实验，定量的验证了电光调Q激光器的优越性。根据速率方程建立了腔倒空脉冲
6、波形与Q开关时间和腔长的数值关系。并实现了脉宽大小恒定为5.50.2 ns的1063 nm Nd:GdVO4腔倒空脉冲激光输出，激光最高运转重频为50 kHz，对应峰值功率为18.2 kW。最后为了减小激光的热效应，在腔倒空实验中采用879 nm LD泵浦源以及GdVO 4/Nd:GdVO4复合晶体，极大的提高了腔倒空激光器的性能，实现了3.80.2 ns的恒定脉宽输出。并在最高重频100 kHz下得到平均功率为 13.1 W的脉冲激光输出。在重频为10 kHz，50 kHz和100 kHz时最高峰值功率分别达到252.6 kW, 65.9 kW和 34.4 kW。关键词：DPSSL ；Nd:
7、GdVO 4 晶体；电光调 Q；腔倒空 哈尔滨工业大学工学硕士学位论文- II -AbstractLaser-diode end-pumped solid-state laser (DPSSL) is focused on for its merits of high efficiency, high beam quality, compact structure and so on. Q-switch technology is the key method to obtain pulsed laser, and is widely used in many industrial and m
8、ilitary fields such as micro-mechanical machining, laser communication, lidar and so on. Electro-optical Q-switched technology is favorable to get high repetition rate, short pulse width and high peak power laser output, because of its advantages of high speed switching time, high on-off ability and
9、 high stablility. Nd:GdVO4 crystal has large absorption and emission cross-section, moderate fluorescence lifetime, high thermal conductivity as well as polarization- laser property, which make it an ideal laser medium under high repetition rate operation. Based on these, this thesis reports the pro
10、perties of laser-diode end-pumped electro-optical Q-switched Nd:GdVO4 laser, including pulse-reflection mode (PRM) and pulse-transmission mode(PTM, cavity-dumped mode).Firstly, the thesis discusses the lasers mode matching and thermal effect of solid-state laser, which are the crucial ingredients of
11、 the lasers power, efficiency and beam quality. According to the relationship between continuous-wave laser power and mode maching, the best ratios of the oscillation modes size and the pumping modes size under different pumping powers are deduced. Based on the analysis of the lasers heat-producing
12、mechanism, the thermal lensing effect is studied. Then the relationship between thermally induced diffraction losses and the pump power as well as the cavity mode size is analyzed. Lastly, this thesis studies the controlling and compensation measures for improving thermal effects. According to the r
13、ate equations for continous-wave pumped solid-state laser, significant parameters for Q-switched laser, such as pulse width, pulse energy and peak power, are inferred. Besides, the optimum coupling reflectivity is also obtained. Under the direction of these theories, this dissertation realizes elect
14、ro-optial Q-switched 1063 nm Nd:GdVO4 laser output in the experiment. The highest operation repetition rate can reach up to 100 kHz, and the peak power is 2.6 kW with a pulse width of 20.6 ns. Meanwhile, the superiority of electro-optical Q-switched laser is verified quantitatively compared to acous
15、to-optical Q-switched laser. Lastly, the numerical relationship between the pulse shape of the cavity-dumped laser and the switching time along with the cavity length is established. In the cavity-dumped experiments, a constant 5.50.2 ns pulse duration laser is obtained. And the 哈尔滨工业大学工学硕士学位论文- III
16、-highest repetition rate is 50 kHz, the corresponding peak power is 18.2 kW. In order to scaling the cavity-pumped laser performance, based on the controlling measures for thermal effects, 879 nm laser diode and GdVO4/Nd:GdVO4 composite crystal are employed in the cavity-pumped experiment. And a constant pulse width of 3.80.2 ns is realized. The highest repetiti
