Berry Monopole Scattering in the Synthetic Momentum Space of a Bilayer Photonic Crystal Slab

Berry monopoles-quantized sources of Berry curvature-are fundamental to topological phases, yet their scattering remains unexplored. Here, we report for the first time the adiabatic scattering of Berry monopoles in a bilayer photonic crystal slab combining one genuine and one synthetic momentum. Two monopoles approach, collide, and scatter within this hybrid parameter space. The process is described by an effective coupled-mode model and confirmed by full-wave simulations. We further propose an experimental scheme using chiral edge states, opening a route to probe monopole interactions in synthetic photonic systems.