Abstract
The phase delays introduced by anisotropic nanounits include propagation phase delay, resonant phase delay and geometric phase delay. Various phase devices can be formed based on the metasurfaces consisting of anisotropic nanounits and the phase devices of the same kind function have different performances because of different working modes. In this paper, metalenses and vortex metalenses are chosen as examples to compare the optical performance of metasurface phase devices based on three kinds of phase compensation techniques. We design separately three kinds of metalenses and vortex metalenses using the cross nanoholes, L-shaped nanohole and V-shaped nanoholes and simulate numerically their intensity and phase distributions. Additionally, the results show the differences among these elements in structure complexity, polarization dependence, working efficiency and phase uniformity. The comparison for three kinds of metalenses clearly shows the merits of different phase compensation techniques and this work must be helpful for expanding the practical applications of metasurfaces.
Highlights
Phase is the main property of light fields and it even determines amplitude, polarization state or other properties of light field
This phase can be differentiated into propagation phase relating to the width of nanounit, resonant phase changing with the length of nanounit and geometric phase depending on the rotation angle of nanounit in terms of the phase modulation mode [10]
This paper aims to construct the phase devices based on three kinds of phase compensation techniques and exhibit the advantages of different techniques through comparing optical performance of these devices
Summary
Phase is the main property of light fields and it even determines amplitude, polarization state or other properties of light field. Phase of light field is usually modified by the phase element through the diffraction effect of element or refraction effect of material, like the wave plate, Soleil-Babinet compensator and Fresnel lens Besides these traditional techniques, recent studies show the phase delay can be controlled by the nanometer units, such as subwavelength gratings [1,2], nanoantennas [3], nanoholes [4,5]. Nanomaterials 2021, 11, 2091 of high-efficiency Bessel beam [26] and metalens [27] These two kinds of metasurface devices show the polarization independence. Geometric phases caused by the rotated nanoscatterers are utilized in the design of Bessel beams [28] and metalens [29,30].
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