image: a The classical Brewster effect limited to a particular incident angle, i.e., Brewster angle θb and the TM polarization, and the birefringence effect of beam splitting due to anisotropy. b Illustration of an anisotropic dielectric MM exhibiting full-polarization omnidirectional Brewster effect, as well as birefringence-free anisotropy as the consequence of effective duality symmetry realized in this dielectric MM.
Credit: by Hao Luo, Jie Luo, Zhihui Zhang, Chao Wu, Quan Li, Wei Liu, Ruwen Peng, Mu Wang, Hongqiang Li, and Yun Lai
Electromagnetic self-duality is one of the most fundamental symmetries of free-space. While in condensed matter like solids and liquids, this self-dual property is broken due to the imbalance between electric and magnetic responses of matter. For decades people have been trying to exploit artificial materials to restore duality symmetry, but so far most studies were limited to theories. Consequently, conventional dielectric solid materials, both natural and artificial, lack electromagnetic self-duality and fail to achieve impedance matching with free space.
This work presents 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 work unveils a practical route to remove the intrinsic polarization dependence and impedance mismatch with free space in general dielectric systems around a certain frequency, which could have important applications such as new radomes resembling free space.
Journal
Light Science & Applications
Article Title
Dielectric Metamaterials with Effective Self-duality and Full-polarization Omnidirectional Brewster Effect