Nonreciprocal diffraction of light based on double-transition-assisted photonic Aharonov-Bohm effect

We propose a nonreciprocal diffraction system based on the photonic Aharonov-Bohm effect. The implementation utilizes the simultaneous up and down photonic transition of Bloch modes in a dielectric grating created by time-harmonic dielectric constant modulation. This double transition process generates opposite effective magnetic fluxes for photons in symmetric and antisymmetric modes, which gives rise to nonreciprocal spatial interference between them. With the broken time-reversal symmetry, this system is possible to exhibit unidirectional highly efficient diffraction, which enables grating-based nonmagnetic isolation and circulation of free space light, and integrates the functions of gratings and isolators.