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Time Crystals in Actively Mode-locked Lasers
Ruiling Weng, Elias R. Koch, Jes\'us Yelo-Sarri\'on, Josep Batle, Neil G. R. Broderick, Julien Javaloyes, Svetlana V. Gurevich
https://arxiv.org/abs/2509.09230

Time Crystals in Actively Mode-locked Lasers
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 …