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Research Paper by Prof. Yi’s Team Published as Cover Article

March 17, 2020      Author: Department of Electronics

Recently, a research team led by Professor Yi Lilin from Department of Electronics, SJTU  published a paper titled “Intelligent control of mode-locked femtosecond pulses by time-stretch-assisted real-time spectral analysis” in Light: Science & Application, a world-famous  research journal in optics  jointly issued by Changchun Institute of Optics and Fine Mechanics and Physics and Nature Publishing Group. The paper was selected as a cover article and reviewed in the column “News & Views”.  The first author is Pu Guoqing, a doctoral student, and the corresponding author is Professor Yi Lilin.


Professor John Dudley (President of European Physical Society, IEEE/OSA Fellow), an expert in nonlinear optics, introduced their research in News & Views of Light: Science & Application. He considered their research innovative, as it pushes the frontier of mode-locked dynamics and could be applied in mode-locked fiber lasers.


Over the past six years, Professor Yi Lilin’s team has been concentrated on the intelligent control of femtosecond mode-locked fiber lasers. In 2019, their finding in intelligent mode-locked fiber lasers was published in the renowned journal Optica and then selected into “Optics in 2019” (a list of yearly achievement in optics) by Optics & Photonics News, a news magazine under the Optical Society of America. Their research on mode-locked fiber laser is partially sponsored by the National Natural Science Foundation of China (61575122).


Mode-locked fiber lasers based on nonlinear polarization evolution can generate femtosecond pulses with different pulse widths and rich spectral distributions for versatile applications through polarization tuning. However, a precise and repeatable location of a specific pulsation regime is extremely challenging. Here, by using fast spectral analysis based on a time-stretched dispersion Fourier transform as the spectral discrimination criterion, along with an intelligent polarization search algorithm, for the first time, we achieved real-time control of the spectral width and shape of mode-locked femtosecond pulses; the spectral width can be tuned from 10 to 40 nm with a resolution of ~1.47 nm, and the spectral shape can be programmed to be hyperbolic secant or triangular. Furthermore, we reveal the complex, repeatable transition dynamics of the spectrum broadening of femtosecond pulses, including five middle phases, which provides deep insight into ultrashort pulse formation that cannot be observed with traditional mode-locked lasers.