【作者】 王成；

【导师】 于欣；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2011， 硕士

【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:GdVO₄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。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。最后研究了管理热效应的措施,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,最窄脉宽为20.2 ns,对应峰值功率达到3.1 kW。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波形与Q开关时间和腔长的数值关系。并在直线腔中实现了脉宽大小恒定为5.5±0.2 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。最后通过采用消光比更高的V形结构谐振腔,将腔倒空脉宽压缩至恒定大小为3.8±0.2 ns。同时采用879 nm LD泵浦源以及GdVO₄/Nd:GdVO₄复合晶体缓解热效应,在重频为80 kHz时得到最高平均功率为13.3 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高达252.6 kW, 65.9 kW和34.4 kW。更多还原

【Abstract】 Laser-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 military 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 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 properties 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 laser’s mode matching and thermal effect of solid-state laser, which are the crucial ingredients of the laser’s power, efficiency and beam quality. According to the relationship between continuous-wave laser power and mode maching, the best ratios of the oscillation mode’s size and the pumping mode’s size under different pumping powers are deduced. Based on the analysis of the laser’s heat-producing 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 rate 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 electro-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 pulse width is 20.2 ns, with a peak power of 3.1 kW. Meanwhile, the superiority of electro-optical Q-switched laser is verified quantitatively compared to acousto-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 5.5±0.2 ns pulse duration laser is obtained. And the 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 3.8±0.2 ns is realized. The maximum average output power of 13.3 W is realized at 80 kHz. At repetition rates of 10 kHz, 50 kHz and 100 kHz, the corresponding peak powers are 252.6 kW, 65.9 kW and 34.4 kW, respectively.更多还原