Coupled pseudo-magnetic field and valley spin in photonic crystals

The topological valley photonic crystal exhibits an intriguing chiral transport of the edge state, attributed to the photonic valley Hall effect. The deformation of the photonic crystal along a uniaxial direction induces a strong synthetic pseudo-magnetic field, leading to the exploration of numerous intriguing phenomena manipulated by magnetic fields. We investigate the coupling between the valley spin and the valley-dependent pseudo-magnetic field in a gradient-deformed photonic crystal. The opposite pseudo-magnetic fields at two inequivalent valleys lead to distinct coupling effects with valley-projected edge states, resulting in a wide photonic bandgap between the dispersion of edge states and bulk bands. The pseudo-magnetic field controls the transmission partition of the edge state at the topological channel intersection within a designed beam splitter. The Aharanov–Bohm-like interferometer composed of gradient photonic crystals is proposed, and the destructive interference resulting from the Fano resonance is demonstrated in an experimental measurement. Our proposal offers a valuable approach for manipulating electromagnetic wave propagation and facilitating the future design of photonic sensors.