Observations of spatiotemporal instabilities of temporal cavity solitons

Temporal cavity solitons (CSs) are pulses of light that can persist in coherently driven passive resonators, such as fiber ring resonators and monolithic microresonators. It has been theoretically predicted that they can exhibit rich instability dynamics, yet experimental observations have remained scarce. Here, we report on the observations of complex spatiotemporal instabilities of temporal CSs in a synchronously driven fiber ring resonator. Through continuous variation of a single control parameter, we observe a string of predicted instabilities, including irregular oscillations (breathing) and chaotic collapses. Beyond a critical point, we find behavior reminiscent of a phase transition: CSs trigger localized domains of spatiotemporal chaos that invade the surrounding continuous wave background. Our findings directly confirm a number of theoretical predictions, and they highlight that complex CS instabilities can play a role in experimental systems.