Nonlinear Control of Electromagnetic Topological Edge States

Topological photonics has emerged recently as a smart approach for realizing robust optical circuitry, and the study of nonlinear effects is expected to open the door for tunability of photonic topological states. Here we realize experimentally nonlinearity-induced spectral tuning of electromagnetic topological edge states in arrays of coupled nonlinear resonators in the pump-probe regime. When nonlinearity is weak, we observe that the frequencies of the resonators exhibit spectral shifts concentrated mainly at the edge mode and affecting only weakly the bulk modes. For a strong pumping, we describe several scenarios of the transformation of the edge states and their hybridization with bulk modes, and also predict a parametrically driven transition from topological stationary to unstable dynamic regimes.This work was partially supported by the Australian Research Council and by the Air Force Office of Scientific Research under Grant No. FA2386-16-1-0002. The numerical calculations are supported by the Russian Science Foundation (Grant No 16-19-10538). Experimental studies of nonlinear response are supported by the Russian Foundation for Basic Research (Grant No. 18-32-20065). Experimental studies of linear response are supported by the Ministry of Education and Science of the Russian Federation (Zadanie No. 3.2465.2017/4.6). The work of A. V. Y. was supported by the Government of the Russian Federation (Grant No. 074-U01) through the ITMO Fellowship