Revealing the Transition Dynamics from Q Switching to Mode Locking in a Soliton Laser

Q switching (QS) and mode locking (ML) are the two main techniques enabling generation of ultrashort pulses. Here, we report the first observation of pulse evolution and dynamics in the QS-ML transition stage, where the ML soliton formation evolves from the QS pulses instead of relaxation oscillatio...

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Bibliographic Details
Published in:Physical review letters 2019-08, Vol.123 (9), p.1, Article 093901
Main Authors: Liu, Xueming, Popa, Daniel, Akhmediev, Nail
Format: Article
Language:English
Subjects:
Computer simulation
Continuous radiation
Dynamics
Lasers
Mode locking
Nanosecond pulses
Relaxation oscillations
Sidebands
Solitary waves
Switching
Ultrafast lasers
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Summary:Q switching (QS) and mode locking (ML) are the two main techniques enabling generation of ultrashort pulses. Here, we report the first observation of pulse evolution and dynamics in the QS-ML transition stage, where the ML soliton formation evolves from the QS pulses instead of relaxation oscillations (or quasi-continuous-wave oscillations) reported in previous studies. We discover a new way of soliton buildup in an ultrafast laser, passing through four stages: initial spontaneous noise, QS, beating dynamics, and ML. We reveal that multiple subnanosecond pulses coexist within the laser cavity during the QS, with one dominant pulse transforming into a soliton when reaching the ML stage. We propose a theoretical model to simulate the spectrotemporal beating dynamics (a critical process of QS-ML transition) and the Kelly sidebands of the as-formed solitons. Numerical results show that beating dynamics is induced by the interference between a dominant pulse and multiple subordinate pulses with varying temporal delays, in agreement with experimental observations. Our results allow a better understanding of soliton formation in ultrafast lasers, which have widespread applications in science and technology.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.123.093901