石墨烯被动锁模全正色散掺镱光纤激光器中的暗脉冲及其谐波

Dark pulses and harmonic mode locking in graphene-based passively mode-locked Yb^(3+)-doped fiber laser with all-normal dispersion cavity

报道了一种基于石墨烯被动锁模的全正色散掺镱环形光纤激光器.在激光器腔中应用激光诱导沉积法制备的石墨烯可饱和吸收体,通过调节抽运光功率和偏振控制器的角度分别得到了明脉冲及其二阶谐波,暗明脉冲对和暗脉冲及其二、三阶谐波这三类不同的脉冲.其中,暗明脉冲对和暗脉冲在基于石墨烯被动锁模的掺镱光纤激光器实验中都是第一次被观察到.本文根据实验结果结合模拟分析了暗脉冲的产生机理,并研究对比了明脉冲谐波和暗脉冲谐波产生的原因.

Graphene has recently been proposed as an attractive material in saturable absorption （SA） applications due to its broad operation range, low saturation power, easy fabrication, high reliability, and quick recovery time. In this paper, we use laser-induced deposition to prepare graphene saturable absorber, and apply it in a mode-locked all-normal-dispersion （ANDi） Yb-doped fiber laser to experimentally investigate different operational states. By adjusting a polarization controller （PC） and the pump power, bright pulses, dark-bright pulse pairs and their second-harmonic pulses, as well as dark pulses and their second, third-harmonic pulses can all be obeserved. In particular, it is the first time to our knowledge to report on the formation of dark-bright pulse pairs, dark pulses and their harmonic mode locking （HML） counterparts in graphene-based passively mode-locked Yb-doped fiber laser with ANDi cavity. Accoding to simulation, the main causes of these pulses are different cavity nonlinear effects which result from the fiber mode-lock members including graphene. Bright pulses, dark pulses and dark-bright pulse pairs are determined both by the laser structure and their own initial signals. Bright pulse harmonic generation is ascribed to the noise gains which form new components. However, it is found that the multiple-time repetition rate of dark pulses is a result of square pulse splitting of each component. This consequence may be of potential application in new type mode-locked fiber lasers.