Ultra-high spectral purity laser derived from weak external distributed perturbation

Ultra-high spectral purity lasers are of considerable research interests in numerous fields such as coherent optical communication,microwave photonics,distributed optical fiber sensing,gravitational wave detection,optical clock,and so on.Herein,to deeply purify laser spectrum with compact size under normal condition,we propose a novel and practical idea to effectively suppress the spontaneous radiation of the laser cavity through weak external distributed perturbation.Subsequently,a laser configuration consisting of a main lasing cavity and an external distributed feedback cavity is proposed.The feedback signal with continuous spatio-temporal phase transition controlled by a distributed feedback structure is injected into the main cavity,which can deeply suppress the coupling rate from the spontaneous radiation to the stimulated emission and extremely purify the laser spectrum.Eventually,an ultra-narrow linewidth on-chip laser system with a side mode suppression ratio greater than 80 dB,an output linewidth of 10 Hz,and a relative intensity noise less than-150 dB/Hz is successfully obtained under normal conditions.The proposed concept in this work provides a new perspective for extreme regulation of laser parameters by using weak external distributed perturbation,which can be valid for various gain-type lasers with wide wavelength bands.

Dynamics of a dispersion-tuned swept-fiber laser

In this paper,we studied the dynamics of a dispersion-tuned swept-fiber laser both experimentally and theoretically.By adding a dispersion compensation fiber and an electro-optic modulator in the laser cavity,an actively mode-locked laser was obtained by using intensity modulation,and wavelength sweeping was realized by changing the modulation frequency.Using a high-speed real-time oscilloscope,the dynamic behaviors of the swept laser were investigated during wavelength switching,static-sweeping cycle,and continuous sweeping,respectively.It was found that the laser generates relaxation oscillation at the start of the sweeping mode.The relaxation oscillation process lasted for about 0.7 ms,and then the laser started to operate stably.Due to the nonlinear effect,new wavelengths were generated in the relaxation oscillation process,which is not beneficial for applications.Fortunately,relaxation oscillation disappears if the laser starts up and operates in the continuous sweeping mode,and the good sweeping symmetry between the positive sweep and negative sweep increases the application potential of the laser.In addition,the instantaneous linewidth is almost the same as that in the static state.These results describe the characteristics of the laser from a new perspective and reveal,to the best our knowledge,the intensity dynamics of such lasers for the first time.This paper provides some new research basis for understanding the establishment process of dispersion-tuned swept-fiber lasers and their potential application in the future.

Analysis of Transmission Characteristics of Tilted Long Period Fiber Gratings With Full Vector Complex Coupled Mode Theory

把联合模式理论基于完整的向量建筑群，详细分析在倾斜的长时期纤维栅栏的传播光谱特征上被做。新传播山峰被观察，它在每座传播山峰的长波长方面旁边位于正常长时期纤维栅栏的传播光谱。新兴的传播山峰对两个相当敏感栅栏倾斜了角度并且包围折射索引，和相应关系被讨论。而且，一个新奇察觉到特征关于倾斜的长时期纤维栅栏被调查，它与传播有关是反响的波长和山峰振幅。