All-dielectric three-element transmissive Huygens’ metasurface performing anomalous refractionPhotonics Research
- Chang Liu, Lei Chen, Tiesheng Wu, Yumin Liu, Jing Li, Yu Wang, Zhongyuan Yu, Han Ye, and Li Yu
- received 08/23/2019; accepted 10/13/2019; posted 10/14/2019; Doc. ID 376213
- Abstract: Metasurfaces have pioneered a new avenue for advanced wave-front engineering. Among various types of metasurfaces, Huygens’ metasurfaces are thought to be a novel paradigm for flat optical devices. Enabled by spectral overlapped electric resonance and magnetic resonance, Huygens’ metasurfaces are imparted with high transmission and full phase coverage of 2π, which makes them capable of realizing high-efficiency wave-front control. However, a defect of a Huygens’ metasurface is that its phase profile and transmissive response are both sensitive to the interaction of neighboring Huygens’ elements inside a metasurface unit. Consequently, the original assigned phase distribution can be distorted. In this work, we illustrate our design strategy of a transmissive Huygens’ metasurfaces performing anomalous refraction. We illustrate the investigation of Huygens’ elements realizing the overlapping between an electric dipole resonance and a magnetic dipole resonance based on the cross-shaped structures. We find that traditional discrete equidistant-phase design method is not enough to realize a transmissive Huygens’ surface due to the interaction between neighboring Huygens’ elements. Therefore, we introduce an extra optimization process on the spacing between the neighboring Huygens’ elements to palliate the phase distortion resulted from the interaction of Huygens elements. Based on this method, we successfully design an unequally-spaced three-element transmissive metasurfaces exhibiting an anomalous refraction effect. The anomalous refractive angle of the designed Huygens’ metasurface is 30°, which exceeds most of the anomalous refractive angles of present transmissive Huygens’ metasurfaces. A transmissive efficiency of 83.5% is numerically calculated at the operating wavelength. The far-field electric distribution shows that about 93% of transmissive light is directed along the 30-degree refractive direction. The deflection angle can be tuned by adjusting the number of Huygens elements in a metasurface unit cell. The design strategies used in this paper can be inspiring for other functional Huygens metasurface scheme.