Abstract
The unidirectional excitation of near-field optical modes is a fundamental prerequisite for many photonic applications, such as wireless power transfer and information communications. We experimentally construct all-electric Huygens and spin metasources and demonstrate anomalous unidirectional excitation of high-k hyperbolic modes in two types of hyperbolic metasurfaces. We use a Huygens metasource to study the unidirectional excitation of hyperbolic bulk modes in a planar hyperbolic metamaterial (HMM). Specifically, unidirectional excitation is the same as that in free space in the vertical direction, but opposite to that in free space in the horizontal direction. This anomalous unidirectional excitation is determined by the anisotropic HMM dispersion. In addition, we use a spin metasource to observe the anomalous photonic spin Hall effect in a planar hyperbolic waveguide. For a near-field source with a specific spin, the guide mode with a fixed directional wave vector is excited due to spin-momentum locking. Because the directions of momentum and energy flows in the HMM waveguide are opposite, the unidirectional excitation of hyperbolic guided modes is reversed. Our results not only uncover the sophisticated electromagnetic functionalities of metasources in the near-field but may also provide novel opportunities for the development of integrated optical devices.
Highlights
IntroductionHyperbolic metamaterials (HMMs), an important class of artificial anisotropic material with hyperbolic isofrequency contours (IFCs), have recently attracted significant attention due to their unique ability to control interactions between light and matter.[1,2,3,4] Tuning the hyperbolic dispersion shape allows light propagation in hyperbolic metamaterial (HMM) to be flexibly controlled to produce all-angle negative refraction,[5,6,7,8] collimation,[9,10] beam splitting,[11,12] and robust transmission.[13,14] Tuning the topological transition of the dispersion from a closed IFC to an open hyperbolic IFC significantly enhances the optical density of states (DOS)
Tuning the topological transition of the dispersion from a closed isofrequency contours (IFCs) to an open hyperbolic IFC significantly enhances the optical density of states (DOS)
We reveal that hyperbolic bulk modes can be used to achieve anomalous unidirectional excitations during near-field excitations of an all-electric Huygens metasource
Summary
Hyperbolic metamaterials (HMMs), an important class of artificial anisotropic material with hyperbolic isofrequency contours (IFCs), have recently attracted significant attention due to their unique ability to control interactions between light and matter.[1,2,3,4] Tuning the hyperbolic dispersion shape allows light propagation in HMMs to be flexibly controlled to produce all-angle negative refraction,[5,6,7,8] collimation,[9,10] beam splitting,[11,12] and robust transmission.[13,14] Tuning the topological transition of the dispersion from a closed IFC to an open hyperbolic IFC significantly enhances the optical density of states (DOS) This has important consequences for the strong enhancement of spontaneous. Related designs can be extended to the fields of natural 2D materials[51,52] and acoustics systems.[31,53,54]
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