Observation of Unidirectional Bulk Modes and Robust Edge Modes in Triangular Photonic Crystals

Abstract

Abstract The valley contrasting physics in photonic systems gives rise to many interesting phenomena such as photonic valley Hall effect and robust valley transport. However, most reported valley photonic crystals are demonstrated in the honeycomb lattice. Here, unidirectional bulk modes and robust edge modes are numerically and experimentally shown in triangular photonic crystals. By switching the phase vortex of an input chiral source, dynamic unidirectional propagation of bulk modes at different valleys is observed. Unidirectional edge modes are also demonstrated on the domain wall between two distinct triangular photonic crystals. In addition, robust edge modes around sharp corners are experimentally confirmed. This work paves the way for the realization of dynamic unidirectional photonic transport and robust valley transport in photonic crystals.