种子注入技术是在高峰值功率的调Q激光器中实现傅里叶变换极限线宽的、稳定的单频输出的最有效方法。由于其优异的频率特性，种子注入激光器被广泛应用于高分辨率光谱分析、非线性光学、激光雷达遥感等领域中。本论文主要围绕种子注入技术展开理论与实验研究。基于注入场方程和调Q速率方程，建立了种子注入激光器多频振荡的理论模型，分析了模式竞争与单纵模选择的动态过程，以及激光在不同注入条件下的脉冲输出特性。理论分析结果指出，激光输出的光谱纯度会随着注入功率的增大和频率失谐量的减小而增大，频率锁定范围会随着注入功率的增大和增益的提高而增大。使用RbTiOPO4（RTP）电光晶体作为腔内相位调制器，设计了高速ramp-fire电路，以实现种子注入激光器的频率锁定。为了获得更高速度和更高精度的调制，应用了一个宽度约为10 μs的3 kV线性斜坡电压，扫描过多个谐振腔的自由光谱范围。这种高速调制方法，可以提高种子注入激光器的脉冲出光时间稳定性。同时，该方法尤其适用于高重复频率的种子注入激光器。此外，通过延迟触发技术，还实现了频率失谐量的精确控制。采用LD侧面泵浦的zigzag板条Nd:YAG晶体和环形腔结构，通过高速ramp-fire锁频技术，实现了大能量的稳定的单频脉冲激光输出。激光器的脉冲能量为67 mJ，脉冲重复频率为20 Hz，脉冲宽度为19 ns，频率稳定性为2 MHz/7min，线宽为1.2倍傅里叶变换极限线宽。同时，还实验研究了该激光器在不同注入功率和频率失谐量条件下的脉冲输出特性，测量了在不同增益条件和注入功率下的频率锁定范围，实验结果与理论分析吻合良好。采用LD端面泵浦的Nd:YAG/Nd:YVO4棒状晶体和环形腔结构，通过高速ramp-fire锁频技术，实现了1 kHz、5 kHz和10 kHz高脉冲重复频率的稳定的单频激光输出。激光器的平均功率在5 W至7.6 W之间，脉冲宽度在10 ns附近，频率稳定性小于2 MHz/min，线宽约为1.2至1.4倍傅里叶变换极限线宽。同时，激光输出具有较高的脉冲出光时间稳定性（15 ns/min）和脉冲能量稳定性（0.3%）。

Injection seeding is the most effective technique of providing Fourier-transform-limited stable single-frequency operation of high-peak-power Q-switched lasers. Owing to their excellent frequency properties, injection-seeded lasers are widely used in various fields, such as high-resolution spectroscopy, nonlinear optics, and lidar remote sensing. In this thesis, we focus on the technique of injection seeding, both in theory and experiment. Based on the injected cavity field equations and the Q-switched rate equations, a theoretical model describing multi-mode oscillating in injection-seeded lasers is established. The dynamic processes of mode competition and single-mode selection in injection seeding are analyzed. The characteristics and performance of the laser output pulse are investigated at various injection conditions. The results of the simulation demonstrate that the spectral purity of the output pulse increases with the increase of injected intensity and with the decrease of detuning frequency, and that the frequency locking range increases for both high injected intensity and high gain. By using a RbTiOPO4 (RTP) electro-optical crystal as the intracavity phase modulator, a fast ramp-fire circuit is built for frequency locking in injection-seeded lasers. For high-speed and high-accuracy modulation, a 3 kV, 10 μs linear voltage ramp is used, sweeping the resonator through multiple free spectral ranges. This high-speed modulation technique improves the timing stability of the laser output pulse, and is especially appropriate to achieve high-repetition-rate operations of injection-seeded lasers. In addition, the detuning frequency is precisely controlled by the delay-fire technique in the experiment. High-energy stable single-frequency operation is achieved by the fast ramp-fire technique in an injection-seeded LD side-pumped Nd:YAG zigzag slab ring oscillator. At 20 Hz, the highest output energy of 67 mJ is obtained with a pulse duration of 19 ns, a frequency stability of 2 MHz/7min, and a linewidth of 1.2 times Fourier-transform-limited. Moreover, the performance of the laser output pulse is experimentally investigated at various injected intensities and detuning frequencies. The frequency locking range is also measured at various injected intensities and gain levels. The experimental results are in good agreement with the theoretical analyses. High-repetition-rate stable single-frequency operations are achieved by the fast ramp-fire technique in injection-seeded LD end-pumped Nd:YAG/Nd:YVO4 rod ring lasers at 1 kHz, 5 kHz, and 10 kHz, respectively. The average output power of 5 W to 7.6 W is achieved with the pulse duration of about 10 ns, frequency stabilities of less than 2 MHz/min, and the linewidth of 1.2 to 1.4 times Fourier-transform-limited. The output pulses of the lasers also have excellent timing stability (15 ns/min) and power stability (0.3%).