Frequency stabilization and tuning of breathing solitons in Si₃N₄ microresonators

Abstract

Dissipative Kerr solitons offer broadband coherent and low-noise frequency combs and stable temporal pulse trains, having shown great potential applications in spectroscopy, communications, and metrology. Breathing solitons are a particular kind of dissipative Kerr soliton in which the pulse duration and peak intensity show periodic oscillation. Here we have investigated the breathing dissipative Kerr solitons in silicon nitride ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mi>Si</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">N</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math> ) microrings, while the breathing period shows uncertainties of around megahertz (MHz) order in both simulation and experiments. This instability is the main obstacle for future applications. By applying a modulated signal to the pump laser, the breathing frequency can be injection locked to the modulation frequency and tuned over tens of MHz with frequency noise significantly suppressed. Our demonstration offers an alternative knob for the control of soliton dynamics in microresonators and paves a new avenue towards practical applications of breathing solitons.