Revealing the behavior of soliton buildup in a mode-locked laser

Abstract

Real-time spectroscopy based on an emerging time-stretch technique can map the spectral information of optical waves into the time domain, opening several fascinating explorations of nonlinear dynamics in mode-locked lasers. However, the self-starting process of mode-locked lasers is quite sensitive to the environmental perturbation, which causes the transient behavior of laser to deviate from the true build-up process of solitons. Here, we optimize the laser system to improve its stability that suppresses the Q-switched lasing induced by the environmental perturbation. We therefore demonstrate the first observation of the entire build-up process of solitons in a mode-locked laser, revealing two possible ways to generate the temporal solitons. One way includes the dynamics of raised relaxation oscillation, quasi mode-locking stage, spectral beating behavior, and finally the stable single-soliton mode-locking. The other way contains, however, an extra transient bound-state stage before the final single-pulse mode-locking operation. Moreover, we have proposed a theoretical modeling to predict the build-up time of solitons, which agrees well with the experimental result. Our findings can bring real-time insights into ultrafast fiber laser design and optimization, as well as promote the application of fiber laser.

Revealing the Buildup Dynamics of Harmonic Mode‐Locking States in Ultrafast Lasers

“…Besides the SPM‐induced instability, dissipative processes are also instrumental in destabilizing the giant pulse because dissipative solitons can contain elements of chaotic dynamics similar to that of a strange attractor in low‐dimensional systems . Multiple theoretical models have been proposed to simulate the starting of mode‐locked lasers, for example, a statistical mechanics model based on the idea of the system crossing an entropic barrier and a two‐step method based on the rate equations and the roundtrip circulating‐pulse method …”

Gigahertz Harmonic Mode‐Locked Fiber Laser Based on Tunable SMS Ultrafast Optical Switch

“…However, the third‐order nonlinearity of real SAs are limited to the low damage threshold and two photon absorption. [ 16,17 ] In addition, the generation process of mode‐locked pulse or high order harmonic when using real material saturable absorber (CNT) has been described in detail by Liu, [ 18–21 ] and through our long‐term experimental observation of single‐mode fiber (SMF)–graded‐index multimode fiber (GIMF)–single‐mode fiber (SMS) mode‐locked fiber optic device, we believe that the generation process of mode lock based on hybrid fiber follows the law of noise initiation, Q‐switching, and mode lock.…”

Intelligent control of mode-locked femtosecond pulses by time-stretch-assisted real-time spectral analysis

“…Combined with a real-time oscilloscope, a TS-DFT operates as a real-time OSA, resolving the issue of the low frame rate in a traditional OSA 20 . In numerous works, TS-DFT-based fast spectral analysis has been used with mode-locked lasers to observe soliton dynamics, including soliton explosions 21,22 , build-up processes of various pulsation regimes [23][24][25] , dissipative solitons 26 , soliton molecules [27][28][29] , sophisticated soliton dynamics [30][31][32][33][34] , and the transition dynamics between pulsation regimes 35,36 . In this article, for the first time, we propose using TS-DFT-based fast spectral analysis as the discrimination criterion to achieve rich modelocking regimes.…”