飞秒被动锁模环形腔掺Er3＋光纤激光器

在考虑增益、损耗、群速度色散、自相位调制、快速可饱和吸收体等各种参数同时作用情况下，分析了非线性偏振旋转效应自启动锁模机理，研究了腔体参数与锁模脉冲之间的关系，并给出飞秒被动锁模环形腔掺Er3＋光纤激光器实验原理。实验采用性能稳定的980nm半导体激光器作为抽运源，高掺杂短长度掺Er3＋光纤作为增益介质，利用非线性偏振旋转锁模技术，得到了稳定的飞秒自起振锁模光脉冲。抽运功率为23mW时，激光器输出锁模脉冲中心波长1552nm，3dB带宽为7.6nm，重复频率14.0MHz，平均输出功率0.43mW，自起振锁模泵浦阈值功率11.5mW,并观测到了稳定的高阶锁模脉冲输出。该激光器与报道过的相同结构光纤激光器相比,自起振泵浦阈值低、脉冲能量高、稳定性好，且频谱边带幅度小。

Femtosecond passively mode-locked Er3+-doped fiber ring laser

The self-starting mode-locked mechanism of nonlinear polarization rotation and the characteristics of the pulses were theoretically investigated with various parameters taken into account,such as gain,loss,group velocity dispersion,self-phase modulation and fast absorber.A fiber ring laser with a small segment of highly Er~(3+)-doped fiber as gain medium,which is pumped by 980nm LD laser and mode-locked by using the nonlinear polarization rotation technique,is successfully demonstrated for the generation of femtosecond pulses.When the laser was pumped at 23mW,stable mode-locked pulses centered at 1552nm with 7.6nm bandwidth and an average output power of 0.43mW was successfully obtained at the repetition rate of 14.6MHz.The threshold power of the self-starting mode-locked pumping is about 11.5mW.The high-order stable mode-locked pulses were also observed experimentally.Compared to the fiber lasers with the similar structures reported previously,the laser presented here has the advantages of very low self-starting pumping threshold,high pulse-energy,small spectral sideband and better stability.