报道了谐振腔长达7.5 m的紧凑型被动锁模激光器，通过谐振腔的折叠设计，整个激光器被压缩为55 cm长，15 cm宽。采用二极管端面抽运Nd:YVO4晶体，经半导体可饱和吸收镜被动锁模后激光再一次通过增益晶体放大后输出。在重复频率为20 MHz时，输出激光脉冲宽度为14.2 ps，最大输出功率6.14 W,输出激光为1064 nm的基横模(TEM00)；单脉冲能量达0.3 μJ。较长的谐振腔保证了良好的光束质量，光束质量因子M2在X方向为1.17，Y方向为1.06，功率不稳定性为0.5%。

A compact passively mode-locked laser with 7.5-m cavity length is reported. The laser is 55 cm in length and 15 cm in width by the resonator folding design. The Nd:YVO4 crystal is end-pumped by the diode laser. The output laser with double-pass of the gain crystal after passively mode locked by semiconductor saturable absorber is obtained. The repetition rate is 20 MHz and the pulse width is 14.2 ps, the average power is 6.14 W and the output laser is TEM00 at 1064 nm. The pulse energy is 0.3 μJ. The quality of laser beam M2 is 1.17 in X direction and 1.06 in Y direction. The power unstability is 0.5%.