For a long time, real-time measurement of complex optical ultrafast processes has been an important topic in the field of ultrafast lasers. However, because the detection speed of electronic equipment is mechanically or electronically limited, it is difficult to obtain non-repetitive transient information. How to achieve real-time measurement of transient physical phenomena has always been a huge challenge for researchers. The emergence of Time-Broadened Dispersive Fourier Transform (TS-DFT) technology overcomes the speed limitation of traditional spectrometers and enables fast real-time spectral measurements. In recent years, based on TS-DFT technology, real-time detection of the ultra-fast instantaneous evolution of optical pulses has been achieved, and a new understanding of the interaction between optical solitons has been achieved. However, the complete dynamics of soliton formation in ultrafast optical systems has not yet been reported.
Recently, the research group of Professor Liu Xueming of Zhejiang University has ingeniously designed a fiber laser system and used TS-DFT technology to observe the complete formation process of solitons, soliton molecules, and harmonic mode-locked solitons in a mode-locked fiber laser for the first time, as well as ultrafast lasers. The complete conversion process from Q-switching to mode locking has achieved an important breakthrough in the field of ultrafast laser nonlinearity. The team discovered two different complete dynamic processes of soliton and soliton molecule formation from enhanced relaxation oscillation to mode-locking and from Q-switching to mode-locking, as well as dispersion waves, gain loss and recovery effects, acoustic resonance and optomechanical interaction. The role played an important role in the formation and stability of harmonic mode locking in the early, middle and late stages of the formation of harmonic mode locking. These studies have contributed to the in-depth understanding of the formation mechanism of soliton in ultrafast lasers, and brought a new understanding of ultrafast transient dynamics and pulse evolution path, which is of great significance to the design and application of ultrashort pulse lasers.
Related research results have been published in journals such as Physical Review Letters, Laser & Photonics Reviews.【Physical Review Letters 121,023905 (2018)、Physical Review Letters 123, 093901(2019)、Laser & Photonics Reviews 13,1800333 (2019)】