Metasurface with broken time reversal symmetry

Abstract

Metamaterials—composed of sub-wavelength structures arranged periodically—have garnered significant attention due to their unique interactions with electromagnetic waves, leading to enhanced antenna performance, perfect absorption, and invisibility effects. Most studies have focused on reciprocal metamaterials with time reversal symmetry, whose application is limited in reciprocal devices, such as clocking and negative index. This dissertation therefore explores the design and application of metamaterials with broken time-reversal symmetry, specifically Tellegen and artificial moving metamaterials, which exhibit real value of cross-coupling between electric and magnetic fields. In this research, a pure Tellegen response is achieved through the combination of gyromagnetic materials and split-ring resonators. This response is characterized by an exceptionally strong Kerr rotation, surpassing that of natural materials by several orders of magnitude. Moreover, the artificial moving coupling is realized with an effective velocity of approximately 0.4c by integrating gyromagnetic materials with chiral structures. Experimental observations revealed that when waves impinge on the slabs from opposite directions, the amplitude of transmission remains identical, imparting merely a phase difference, while the reflection properties remain unchanged. For practical applications, the gyromagnetic materials were integrated with chiral structures to create a high-contrast non-reciprocal magnetic-optical metasurface. Experimental results demonstrated that in the forward direction, the metasurface predominantly transmits energy in the zeroth order, whereas in the backward direction, energy is predominantly scattered to the first order, effectively blocking zeroth order transmission. This design is realized by a passive method and is valid for arbitrary polarization. This dissertation advances the understanding of non-reciprocal metamaterials by presenting innovative designs and experimental validations. Tellegen materials provide a powerful platform for the experimental investigation of axion electrodynamics, advancing fundamental physics. Moving material provides a new platform to investigate relativity theory. They also enhance potential applications such as gyrators and isolators. Future research could focus on exploring different metamaterial designs, thereby improving efficiency and broadening applications.