Topological Photonic Chiral Mode Converters

Topological photonic states are immune to structural defects and perturbations, which are considered as a promising solution for realizing robust integrated optical devices. As an essential photonic component, the chiral mode converter, which can directionally switch the modes of photonic states, plays a key role in integrated photonics. However, there is no way to realize topological photonic chiral mode converters. Here, a method is proposed to realize topological photonic chiral mode converters by dynamically encircling exceptional points in topological photonic systems. The device can directionally switch modes of topological photonic states and endow the mode converter with topology protection. Chiral dynamic behavior emerges between the two topological states due to the nonadiabatic transitions within the non-Hermitian topological photonic system. The topological photonic chiral mode converter is robust against random perturbations of coupling strengths. The realization of a topological chiral mode converter endows topology protection into traditional photonic devices and will promote the practical applications of topological photonic states, such as mode multiplexers and optical isolators.