Nonlinear topological photonics: from SSH to HOTIs

The Su-Schrieffer-Heeger (SSH) lattice represents a paradigmatic one-dimensional (1D) topological model, which has been widely employed in topological photonics and realized with versatile platforms including nanophotonics, plasmonics, and quantum optics [1–12]. In this talk, I will briefly discuss its topological nature and the new understanding of sub-symmetry protected topological states [13]. I will then focus on two examples from our recent work based on the 1D SSH photonic platform. One is in the fundamental side - about nonlinear control of topological edge states and tuning of parity-time symmetry using laser-written photonic lattices [10, 11]; the other is more towards application - about topologically tuned terahertz confinement in a nonlinear photonic chip [12]. Nonlinear control of topological states in higher-order topological insulators (HOTIs) will also be discussed, including the recent demonstrations of nonlinear control of photonic higher-order topological bound states in the continuum in two-dimensional SSH lattices [14] and nonlinearity-induced rotation of photonic p-orbital corner states in Kagome-type HOTIs [15]. I will end the talk with a brief outlook of topological photonics being an active field continuously in the coming decade [16].