Artificial Cnoidal Wave Breathers in Optical Microresonators

• Yiran Gao, Jian Dai, Zhonghan Wu, Junqiu Liu, tian zhang, Wei Sun, Anni Liu, and Kun Xu
• received 02/20/2024; accepted 05/01/2024; posted 05/02/2024; Doc. ID 519666
• Abstract: Breathers are localized structures that undergo a periodic oscillation in their duration and amplitude. Optical microresonators, benefiting from their high-quality factor, provide an ideal test bench for studying breathing phenomena. In a monochromatically pumped microresonator system, intrinsic breathing instabilities are widely observed in the form of temporal dissipative Kerr solitons which only exist in the effectively red-detuned regime. Here, we demonstrate a novel bichromatic pumping scheme to create compulsive breathing microcombs via respectively distributing two pump lasers at the effectively blue- and red- detuned sides of a single resonance. We experimentally discover the artificial cnoidal wave breathers and molecular crystal-like breathers in a photonic chip-based silicon nitride microresonator, and theoretically describe their intriguing temporal dynamics based on the bichromatic pumping Lugiato-Lefever equation. In particular, the corresponding breathing microcombs exhibit diverse comb line spacing ranging from 2 to 17 times the free spectral range of the microresonator. Our discovery not only provides a simple yet robust method to harness microcombs with reconfigurable comb line spacing, but also reveals a new class of breathing waves in driven dissipative nonlinear systems.