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Prof. Zhan Li’s Team First Captures Subharmonic Entrainment Breather Solitons

October 30, 2020      Author:

Recently, Prof. Zhan Li’s research team from the School of Physics and Astronomy, SJTU made significant progress in the field of ultrafast laser. They captured the subharmonic entrainment breather solitons in ultrafast lasers for the first time in human history. The research result was published in Physical Review Letters, titled Subharmonic Entrainment Breather Solitons in Ultrafast Lasers”.

The team developed a set of single point measurement technology which can precisely measure superfast time events from as (10-18s) to ps (10-12s). This technology is called technology that helps to capture the relative time and position between adjacent solitons, providing evidence for the subharmonic effect of the breather solitons. Besides, the research team also found that the subharmonic effect can significantly improve the stability of breather solitons and largely reduce the noise level so as to efficiently improve the performance of breather soliton laser, which is a vital progress in the development of breather solitons laser stabilization and the application of optical frequency comb.

Xian Tianhao, doctoral student from School of Physics and Astronomy, is the first author, and professor Zhan Li is the corresponding author. This research has received support from National Nature Science Foundation.



We study theoretically and experimentally the subharmonic entrainment (SHE) breather soliton in mode-locked lasers for the first time, in which the ratio of the breather period to the round-trip time is an integer. We build a non-Hermitian degeneracy map of breather soliton, and illustrate that SHE arises between the two exceptional points (EPs). We obtain SHE at the ratio of 20, observe the evolution of breather soliton when tuning the gain and/or cavity loss, and prove that this phenomenon can improve the stability of breather soliton. Our research brings insight into the EP physics of ultrafast lasers and makes the mode-locked laser a powerful test bed for non-Hermitian degeneracy, which may open a new course in ultrafast laser research.



Author: Zhan Li

Affiliation: School of Physics and Astronomy, SJTU

Translated by Han Yueyue