Observation of temporal cavity solitons in a synthetic photonic lattice

The implementation of synthetic dimensions in a physical system is a seminal concept that provides ideal test-beds for exploring complex dynamics. The key idea is to couple and expand upon the system’s degrees-of-freedom so as to permit exploration of physical phenomena associated with higher dimensionality [1] – [6] . Taking benefits from stability and reliability of optical platforms, this concept has been successfully implemented in photonics to unveil intricate behaviours, including Bloch oscillations [1] , Anderson localization [2] or quantum random walks [3] . Recently, synthetic frequency dimensions have also been investigated in the context of coherently-driven optical resonators, in particular with direct analogy with solid-state physics, as well as for optical frequency combs and topological photonics applications [4] – [6] . In such systems, the synthetic frequency dimension is encoded directly into the optical resonator by means of an intra-cavity phase modulation. The resulting "photonic lattice" acts as a strong potential for the circulating light, modifying dynamically the resonance condition along the cavity length and thus revealing the existence of band structures [4] .