Dielectric Metamaterials with Effective Self-duality and Full-polarization Omnidirectional Brewster Effect

Abstract Conventional dielectric solid materials, both natural and artificial, lack electromagnetic self-duality and fail to achieve impedance matching with free space. Here, we present a class of dielectric metamaterials that exhibit effective self-duality and also enable full-polarization omnidirectional impedance matching, thereby extending the Brewster effect across all incident angles and polarizations. The self-duality eliminates birefringence despite significant anisotropy in dispersion. Meanwhile, the full-polarization omnidirectional Brewster effect ensures near-zero reflection on interfaces with free space, regardless of incidence wavefront and polarization. These unique properties establish electromagnetic equivalence with "stretched free space" in transformation optics, as substantiated through full-wave simulations and microwave experiments. Our findings open a pathway for realizing unprecedented polarization-independence and omnidirectional impedance-matching characteristics in pure dielectric solids.