Prof.  Weicheng  Chen
School of Physics and Optoelectronic Engineering, Foshan University,  China

Title: Intelligent manipulation of polarized soliton generation and its nonlinear dynamics in phase space

Abstract:

On-demand pulse generation and its nonlinear dynamics in mode-locked fiber lasers remains a technical challenge, which has long been a primary topic in nonlinear science. Current research on on-demand pulse generation focuses primarily on intensity-dependent scalar construction methods. These methods inherently yield arbitrary members of a general solution set characterized by identical spectral or temporal information, leading to inadequate evaluation of mode-locked pulses. Meanwhile, investigating on intensity-dependent nonlinear dynamics, which can potentially alters pulse performances, results in pulse dynamics that span distinct solution sets. To address these difficulties, we propose an intelligent mode-locking technique to generate controllable polarized solitons and reveal their nonlinear dynamics from a phase space perspective, which can advance the understanding of on-demand pulse eigenstate generation and provide a new perspective for nonlinear science.

Using the constraints of identical spectra and autocorrelation traces, we employ a customized loss function to intelligently evaluate soliton properties from a fiber laser. This approach maps the mode-locking region on the Poincaré sphere at a fixed pump power by first performing a coarse polarization scanning to determine the region range and then a refined one to record pulse states. Thus, a degenerate soliton solution set is experimentally established within a mode-locking region and a mapping is also achieved between the scanning voltages of the intracavity electronic polarization controller and the pulse's state of polarization. Within the mode-locking region, we further create controllable polarized soliton states with either fixed ellipticity or fixed azimuth, whose states of polarization are characterized either by varying along parallels at fixed ellipticity or by rotating along meridians at fixed azimuth on the Poincaré sphere. Subsequently, we manipulate intracavity polarization settings to reveal their nonlinear dynamics in phase space within the mode-locking region, such as bifurcation, limit cycle, precession, and chaos. These dynamics are characterized in the phase diagram by pitchfork bifurcation, circular trajectory, the precession of limit circles, and the disorder of the phase evolution, respectively.

Our work provides an automatic mode-locking approach for the controllable generation of polarized solitons by combining intensity-dependent information constraints with polarization manipulation and a new perspective for nonlinear science, extending the focus from intensity space to phase space.

Biography:

Chen Weicheng, Ph.D., Professor, Master's Supervisor, Joint Ph.D. Supervisor at Macau University of Science and Technology. He has led 3 projects funded by the National Natural Science Foundation of China (including 2 General Projects and 1 Young Scientist Project), 2 projects under the Guangdong Basic and Applied Basic Research Foundation (including 1 Regional Joint Fund and 1 General Project), 1 project under the Guangdong Key Construction Discipline Research Capacity Improvement Program.