Flexible light manipulation in non-Hermitian frequency Su-Schrieffer-Heeger lattice.

Recently, studies on non-Hermitian topologic physics have attracted considerable attention. The non-Hermitian skin effect (NHSE), as a remarkable phenomenon in the non-Hermitian lattice, has been demonstrated in coupled ring resonators and photonic mesh lattices. However, there is a scarcity of work on the realization of NHSEs in synthetic dimensions, owing to inaccessible anisotropic coupling. This limits the potential for exploring non-Hermitian topologic physics in on-chip integrated optical systems. In this work, we implement a non-Hermitian Su-Schrieffer-Heeger topologic insulator in the synthetic frequency dimension, and the NHSE and topologic edge state are manifested. Furthermore, we demonstrate that the exotic chiral Zener tunneling can also be realized. Our system provides a versatile platform to explore and exploit non-Hermitian topologic physics on a chip and can have impacts on flexible light manipulation in frequency domains.