Abstract
Unidirectional radiation is of particular interest in high-power lasing and optics. Commonly, however, it is difficult to achieve a unidirectional profile in such a system without breaking reciprocity. Recently, assisted by metamaterials without structural symmetry, antennas that radiate asymmetrically have been developed, hence providing the possibility of achieving unidirectionality. Nevertheless, it has been challenging to achieve extremely high radiation asymmetry in such antennas. Here, it is demonstrated that this radiation asymmetry is further enhanced when magnetic plasmons are present in the metamaterials. Experimentally, it is shown that a thin metamaterial with a thickness of ≈λ(0)/8 can exhibit a forward-to-backward emission asymmetry of up to 1:32 without any optimization. The work paves the way for manipulating asymmetric radiation by means of metamaterials and may have a variety of promising applications, such as directional optical and quantum emitters, lasers, and absorbers.