Time Crystals in Actively Mode-locked Lasers
Abstract
We report the first experimental observation of discrete time-crystal phases and crystallites in an actively mode-locked semiconductor laser. By tuning either the bias current or the modulation frequency, the system undergoes a spontaneous symmetry-breaking transition from the harmonically mode-locked state towards robust, highly coherent time-crystal states that persist indefinitely. Two equivalent time-crystal configurations, shifted by one driving period, can coexist as domains separated by sharp, long-lived boundaries analogous to domain walls. The phenomenon is quantitatively reproduced by a time-delayed model adapted to the large gain and losses of semiconductor systems. Our findings demonstrate that mode-locked semiconductor lasers offer a readily accessible platform to explore and control non-equilibrium phases of light, enabling practical implementations of time-crystal physics in photonic systems.
Cite
@article{arxiv.2509.09230,
title = {Time Crystals in Actively Mode-locked Lasers},
author = {Ruiling Weng and Elias R. Koch and Jesús Yelo-Sarrión and Josep Batle and Neil G. R. Broderick and Julien Javaloyes and Svetlana V. Gurevich},
journal= {arXiv preprint arXiv:2509.09230},
year = {2025}
}
Comments
7 pages, 7 figures