通过延长激光器环形腔腔长，利用高浓度掺杂的单模掺镱光纤，搭建了超低重复频率、全正色散结构的半导体可饱和吸收镜被动锁模光纤激光器。激光器的中心波长、重复频率、平均功率及单脉冲能量分别为1 064 nm，281.5 kHz,11 mW和39 nJ。为了稳定中心波长,实现自启动，激光器腔体内接入了一个带通滤波器。该激光器运行稳定，无调Q不稳定现象,极大减小了半导体可饱和吸收镜被损坏的机会。

An ultralowrepetitionrate, allnormaldispersion fiber laser is proposed which is passively modelocked by an SESAM (semiconductor saturable absorber mirror) with ultra long cavity length and high concentration single mode ytterbiumdoped fiber. The central wavelength, repetition rate, average power and energy of a single output pulse are 1 064 nm, 281.5 kHz, 11 mW and 39 nJ, respectively. A bandpass filter is employed in the cavity to stabilize the central wavelength and realize selfstart operation. The laser operates stably and has no Qswitching instabilities, which greatly reduces the damage probability of the SESAM.