Revealing the Transition Dynamics from Q Switching to Mode Locking in a Soliton Laser
Date
2019
Authors
Liu, Xueming
Popa, Daniel
Akhmediev, Nail
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American Physical Society
Abstract
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 quasicontinuous-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.
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Physical Review Letters
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Journal article
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Open Access
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