Fast encirclement of an exceptional point for highly efficient and compact chiral mode converters

Exceptional points (EPs) are degeneracies where eigenvalues and eigenstates of a non-Hermitian system coalesce. Encircling EPs dynamically switches chiral modes; the final state depends on the encirclement direction. Conventional methods require slow, adiabatic parameter evolution. This research shows that fast parametric evolution along the Hamiltonian's parameter space boundary relaxes this constraint, enabling highly efficient and compact asymmetric mode converters. Experiments using a 57 µm double-coupled silicon waveguide system demonstrate near-unity transmission efficiency at 1550 nm, paving the way for high-efficiency, highly integrated chiral mode switching.

Xiaoqian Shu, Aodong Li, Guangwei Hu, Jian Wang, Andrea Alù, Lin Chen