An Ultra-Wideband Double-Layer Microwave Metalens with Reverse Dispersion Characteristic

Microwave meta-lenses (or metasurface lenses) provide an exciting platform to develop a series of novel devices and systems such as transmit array antennas, flat retro-reflectors and compact imagers, etc. Up to now, to design an ultra-broadband plasmonic metalens with excellent focusing performances (such as high focusing efficiency or large numerical aperture) is still a great challenge especially in low frequency microwave regime. In this paper, an ultra-thin and ultra-broadband microwave metalens with a working bandwidth ranging from 13 to 18GHz is designed and its focusing performances are studied, presented and analyzed by a full-wave simulation studio (the relative bandwidth is 33.3% according to simulations, thickness is only 0.1λO, λO is the wavelength of 13GHz). Numerical simulations indicate that the focal length of the double-layer microwave metalens increases linearly along with increased working frequency which demonstrates a reverse dispersion property. High focusing efficiency range from 20%- 60°/ (the average value is above 40%) in the entire working bandwidth is achieved both with a high numerical aperture of 0.7 on average (NA=0.7). The presented studies can be beneficial to the development of broadband microwave metalenses with high- performance focusing and are promising for some applications in metalens-based microwave devices.