Mechanisms of 2π phase control in dielectric metasurface and transmission enhancement effect

Metasurfaces, two-dimensional structures composed of nanoantennas in an army configuration, can be used to fully control electromagnetic waves, which requires a 2 pi phase shift. Herein, we apply the silicon metasurface as an example to interpret the mechanisms of full 2 pi phase coverage. It is found that the mechanism varies from Fabry-Perot resonance to Mie resonance as the period increases for a metasurface with certain height. Particularly, there is a transition region between these two types of resonance. We present the corresponding periods and wavelength regions of the different mechanisms when considering the phase-gradient mctasurfacc with at most three diffraction orders. Moreover, the transmission enhancement of metasurface is investigated. The transmission efficiency can be effectively improved when the nanoantcnna is changed from a uniform structure to a gradient-index one. We ex pect that the results can simplify the design process and provide a reference for the future design of all-dielectric mctasurface with 2 pi phase control. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement