Bichromatically pumped artificial cnoidal wave breathers in optical microresonators

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.