Highly Efficient and Broadband Achromatic Transmission Metasurface to Refract and Focus in Microwave Region

Abstract

Achromatic devices have wide application prospects in radar and imaging fields. However, chromatic aberration and limited bandwidth restrict their development. Moreover, broadband and highly efficient achromatic devices working in transmission mode are still difficult to realize. In this paper, broadband highly efficient achromatic transmission in the microwave region by a metasurface is achieved. First, the ideal dispersion conditions of achromatic meta-atoms are given. Then, a polarization selective grating metasurface and a split ring slot metasurface are designed using the transfer matrix method and equivalent circuit theory, respectively. The former is used to control phase characteristics while the latter enables controlling dispersion. Phase and dispersion can be controlled independently by cascading them and any phase curve can be designed as is desired. In order to verify the strategy, an achromatic deflector and an achromatic lens are designed and samples are fabricated. The experimental results show that the deflector can realize achromatic refraction from 9.3 to 12.3 GHz with average efficiency 77.5% and the lens can realize achromatic focusing from 9.8 to 12.2 GHz with average efficiency 78.9%, respectively. The experimental results are in good agreement with theory. The findings provide valuable strategy for achromatic devices design, which can be widely applied.

Achromatic Broadband Multi‐Layer Diffraction Mode Multiplexing

“…There has been a few progress reported for broadband achromatic optical devices by tuning the resonance phase, propagation phase, or geometric phase of the meta‐surfaces structure. [ 31–34 ] For example, Sun et al. developed broadband diffractive meta‐lenses using multi‐layer diffractive structures composed of materials with different refractive indices.…”

“…There has been a few progress reported for broadband achromatic optical devices by tuning the resonance phase, propagation phase, or geometric phase of the meta-surfaces structure. [31][32][33][34] For example, Sun et al developed broadband diffractive meta-lenses using multi-layer diffractive structures composed of materials with different refractive indices. [35] Chen et al proposed an ultra-broadband and high-efficiency meta-mirror without reflection and chromatic aberration based on the multi-resonant Lorentzian model.…”

Liquid crystal embedded dielectric metalens for active focal length tuning at the microwave range

“…Metasurfaces [4][5][6] , artificial electromagnetic microstructures with freely designed functionalities, are recently introduced to fabricate the microwave lenses, i.e., metalenses. By carefully tailoring the resonant property of the meta-unit to control the amplitude, phase and frequency of the electromagnetic wave, high numerical aperture (NA) metalens, ultrathin flat metalens, broadband achromatic metalens and far-field subwavelength imaging have been achieved [7][8][9][10] . To realize large phase shift and high transmission, many of them are composed of multilayer metallic resonator arrays 7,[11][12][13] , which add to the design and fabrication complexity.…”

Broadband achromatic electromagnetic beam control based on reflective metamaterial

“…[11][12][13], negative refraction [14], zero refractive index [15], etc. Using metasurfaces to control electromagnetic waves, many new functional devices have been realized, such as holographic projection [16], radar stealth [17], absorbers [18,19], deflectors [20], beam splitters [21], etc.…”

“…In 2017, Wang et al [24] realized an achromatic lens in the wavelength range of 1200-1680 nm based on the resonant phase [25] and the Pancharatnam-Berry (PB) phase, using metal nanostripes for phase control [26]. In 2022, Ji et al [20] realized the achromatic deflector from 9.3 GHz to 12.3 GHz using the theory of transfer matrix method and equivalent circuit respectively. For achromatic metasurfaces, research in the terahertz band is not extensive.…”