大模场面积光子晶体光纤激光器展宽脉冲锁模域的束缚态运转

Bound State Operations in Stretched-Pulse Mode-Locking Large-Mode-Area Photonic-Crystal-Fiber Laser

实验研究了大模面积光子晶体光纤飞秒激光器在近零色散点展宽脉冲锁模的束缚态运转。获得了双脉冲束缚态锁模,以及脉冲间隔不相等的多脉冲束缚态锁模,实验发现束缚态的子脉冲间距具有随机性。通过建立光纤锁模激光器的数值模型,分析了激光器束缚态锁模建立的动力学过程,在一定抽运强度下,激光器存在多个稳态,或者单脉冲运转,或者子脉冲间隔不相等的束缚态运转,这取决于锁模建立阶段半导体可饱和吸收镜(SESAM)对噪声信号的随机提取。并提出了抑制束缚态的方法,模拟得出此项技术可直接获得的最大单脉冲能量为19.6 nJ,考虑到40%左右的压缩损耗,可得到压缩至76 fs的最短脉冲,单脉冲能量为11.8 nJ。数值模拟结果能很好的与实验相符合。

Bound states in a stretched-pulse large-mode-area photonic crystal fiber mode-locking laser operating in the vicinity of zero dispersion regime is demonstrated, where the double pulse and multi-pulse bound state modelocking are obtained. The experiment shows that the separation between sub-pulses is unequal with some randomicity. A numerical model of the mode-locked fiber laser is established and the simulations show that the laser can operate either with single-pulse or with multi-pulse in a certain pump power range depending on semiconductor saturable absorber mirror （SESAM）, which selects signal randomly from noise. And the characteristic of the multipulse bound states and randomicity of the distance between sub-pulses are researched. The results can be used to enhance the single pulse energy, which indicated that the highest pulse energy of 19.6 nJ can be obtained with a compressed pulse duration of 76 fs and a reduced pulse energy of 11.8 nJ due to about 40% compression loss. The numerical simulation agrees well with the experiment.