Dynamic gain driven mode-locking in GHz fiber laser  

作　　者：Xuewen Chen Wei Lin Xu Hu Wenlong Wang Zhaoheng Liang Lin Ling Yang Yang Yuankai Guo Tao Liu Dongdan Chen Xiaoming Wei Zhongmin Yang 

机构地区：[1]School of Physics and Optoelectronics,State Key Laboratory of Luminescent Materials and Devices,Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices,Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques,South China University of Technology,Guangzhou,China [2]Research Institute of Future Technology,South China Normal University,Guangzhou,Guangdong,China

出　　处：《Light(Science & Applications)》2024年第11期2715-2725,共11页光（科学与应用)（英文版）

基　　金：supported by National Natural Science Foundation of China(NSFC)(62375087);NSFC Development of National Major Scientific Research Instrument(61927816);Key-Area Research and Development Program of Guangdong Province(2023B0909010002);Introduced Innovative Team Project of Guangdong Pearl River Talents Program(2021ZT09Z109);Natural Science Foundation of Guangdong Province(2021B1515020074).

摘　　要：Ultrafast lasers have become powerful tools in various fields,and increasing their fundamental repetition rates to the gigahertz(GHz)level holds great potential for frontier scientific and industrial applications.Among various schemes,passive mode-locking in ultrashort-cavity fiber laser is promising for generating GHz ultrashort pulses(typically solitons),for its simplicity and robustness.However,its pulse energy is far lower than the critical value of the existing theory,leading to open questions on the mode-locking mechanism of GHz fiber lasers.Here,we study the passive mode-locking in GHz fiber lasers by exploring dynamic gain depletion and recovery(GDR)effect,and establish a theoretical model for comprehensively understanding its low-threshold mode-locking mechanism with multi-GHz fundamental repetition rates.Specifically,the GDR effect yields an effective interaction force and thereby binds multi-GHz solitons to form a counterpart of soliton crystals.It is found that the resulting collective behavior of the solitons effectively reduces the saturation energy of the gain fiber and permits orders of magnitude lower pulse energy for continuous-wave mode-locking(CWML).A new concept of quasi-single soliton defined in a strongly correlated length is also proposed to gain insight into the dynamics of soliton assembling,which enables the crossover from the present mode-locking theory to the existing one.Specifically,two distinguishing dynamics of Q-switched mode-locking that respectively exhibit rectangular-and Gaussian-shape envelopes are theoretically indicated and experimentally verified in the mode-locked GHz fiber laser through the measurements using both the standard real-time oscilloscope and emerging time-lens magnification.Based on the proposed criterion of CWML,we finally implement a GDR-mediated mode-locked fiber laser with an unprecedentedly high fundamental repetition rate of up to 21 GHz and a signal-tonoise ratio of 85.9 dB.

关 键 词：FIBER mode LOCKING 

分 类 号：TN248[电子电信—物理电子学]