Real-time observation of soliton pulsation in net normal-dispersion dissipative soliton fiber laser

We present experimental observations of soliton pulsations in the net normal-dispersion fiber laser by using the dispersive Fourier transform(DFT) technique. According to the pulsating characteristics, the soliton pulsations are classified as visible and invisible soliton pulsations. The visible soliton pulsation is converted from single-into dual-soliton pulsation with the common characteristics of energy oscillation and bandwidth breathing. The invisible soliton pulsation undergoes periodic variation in the spectral profile and peak power but remains invariable in pulse energy. The reason for invisible soliton pulsation behavior is periodic oscillation of the pulse inside the soliton molecule. These results could be helpful in deepening our understanding of the soliton pulsation phenomena.

Spatio-spectral dynamics of soliton pulsation with breathing behavior in the anomalous dispersion fiber laser

We have numerically and experimentally observed the soliton pulsation with obvious breathing behavior in the anomalous fiber laser mode-locked by a nonlinear polarization rotation technique.The numerical study of the soliton pulsation with breathing behavior was analyzed through the split-step Fourier method at first,and it was found that the phase difference caused by the polarization controller would affect the breathing characteristics.Then,taking advantage of the dispersive Fourier transform technique,we confirmed the breathing characteristic of soliton pulsation in the same fiber laser as the simulation model experimentally.These results complement the research on the breathing characteristic of soliton pulsation.

Transient breathing dynamics during extinction of dissipative solitons in mode‑locked fiber lasers

The utilization of the dispersive Fourier transformation approach has enabled comprehensive observation of the birth process of dissipative solitons in fiber lasers.However,there is still a dearth of deep understanding regarding the extinction process of dissipative solitons.In this study,we have utilized a combination of experimental and numerical techniques to thoroughly examine the breathing dynamics of dissipative solitons during the extinction process in an Er-doped mode-locked fiber laser.The results demonstrate that the transient breathing dynamics have a substantial impact on the extinction stage of both steady-state and breathing-state dissipative solitons.The duration of transient breathing exhibits a high degree of sensitivity to variations in pump power.Numerical simulations are utilized to produce analogous breathing dynamics within the framework of a model that integrates equations characterizing the population inversion in a mode-locked laser.These results corroborate the role of Q-switching instability in the onset of breathing oscillations.Furthermore,these findings offer new possibilities for the advancement of various operational frameworks for ultrafast lasers.

Detection of transient mode-locking dynamics for a femtosecond Yb:KGW laser

The evolution dynamics of mode locking for a solid-state femtosecond Yb:KGW laser is demonstrated and detected with time-stretch dispersive Fourier transform(DFT)technique for the first time,to the best of our knowledge.The Yb:KGW laser is constructed first with a classical X-shaped cavity,and SESAM-assisted Kerr lens mode locking is obtained.Then,a DFT device is built to record the buildup and extinction dynamics of the mode-locked laser.The results suggest that the time of extinction is slightly shorter than the buildup time and both of them experience complex transitions.The results indicate that DFT could also be suitable to detect the transient buildup and extinction process in solid-state lasers,which would help investigate both the evolution of mode locking and characteristics determination for solid-state lasers.

Processing of Calamine with Modern Analytical Techniques:Processed with Huanglian Decoction(黄连汤)and Sanhuang Decoction(三黄汤)

Objective： To determine the pyrolysis characteristics of calcined and processed calamine, qualitatively and quantitatively compare the contents of related elements, morphology and functional groups of the pyrolysis products dried at different heating temperatures and explore the critical temperature and the optimal drying temperature for the process of calamine with Huanglian Decoction（HLD, 黄连汤） and San Huang Decoction（SHD, 三黄汤）. Methods： Pyrolysis products were prepared by programmable and constantly heating the calcined and processed calamine to or at different heating temperatures. Thermogravimetry（TG） was used to test their pyrolysis characteristics. Fourier transform infrared spectroscopy and scanning electron microscopeenergy dispersive spectrometer were used to determine their morphology, functional groups and element contents. Page model was used to investigate the constant drying kinetics of processed calamine. Results： The adding of HLD or SHD to calcined calamine（CC） can slow its weight loss in drying pyrolysis process. The temperature ranges where HLD and SHD can affect its weight loss were 65–150 ℃ and 74–180 ℃, respectively. The drying temperature was optimized as 90 ℃. The drying kinetic for the processed calamine fits Page model shows good linearity. Conclusions： The critical temperature and the optimal drying temperature where HLD and SHD can affect the weight loss rate in the process of calamine were explored using the theories and methods of both biophysical chemistry and processing of Chinese materia medica. This work provides a good example for the study of the process of other Chinese medicines using modern analytical techniques.

Dynamics of multi-state in a simplified mode-locked Yb-doped fiber laser

The dispersive Fourier transform technique provides feasibility of exploring non-repetitive events and the buildup process in ultrafast lasers.In this paper,we report a new buildup process of dissipative solitons in a simplified mode-locked Yb-doped fiber laser,which includes more complex physics stages such as the Q-switching stage,raised and damped relaxation oscillation stages,noise-like stage,successive soliton explosions stage,and soliton breathing stage.Complete evolution dynamics of noise-like pulse and double pulse are also investigated with dispersive Fourier transform.For the noise-like pulse dynamics process,it will only experience the Q-switching and relaxation oscillation stages.In the case of dissipative soliton and noise-like pulse,the double pulse buildup behavior is manifested as the replication of individual pulses.A weak energy migration occurs between two pulses before reaching steady state.Meanwhile,real-time mutual conversion of the dissipative soliton and noise-like pulse has been experimentally observed,which appears to be instantaneous without extra physical processes.To the best of our knowledge,this is the first report on these physical phenomena observed together in a mode-locked fiber laser.The results further enrich the dynamics of mode-locked fiber lasers and provide potential conditions for obtaining intelligent mode-locked lasers with controllable output.