Abstract
The design mentality of an optimal metalens model, based on the electromagnetic susceptibility, a synthesis of subwavelength-thick metasurfaces (MSs) is presented in this paper. First, based on the finite difference method of generalized sheet transition conditions, the surface susceptibility function of the MS with spatial discontinuities can be determined. Then, the paper analyzed the remaining corresponding physical field conditions for the scale of metalens. In order to adapt to the physical limitations encountered in the near-field focusing of the metalens, a standard parabolic phase design is proposed in this paper, and its upsides and downsides of the two-phase processing in different aspects are compared. Using COMSOL software with numerical simulation, it can be seen that the standard design can easily obtain high resolution in the near field, while the focusing effect is more stable when the focal length is small by the parabolic phase design.
Highlights
The lens is the most basic element of the optical system, and its history can even be traced back to the ancient crystal ball used for divination and “seeing”
In order to adapt to the physical limitations encountered in the near-field focusing of the metalens, a standard parabolic phase design is proposed in this paper, and its upsides and downsides of the two-phase processing in different aspects are compared
Using COMSOL software with numerical simulation, it can be seen that the standard design can obtain high resolution in the near field, while the focusing effect is more stable when the focal length is small by the parabolic phase design
Summary
The lens is the most basic element of the optical system, and its history can even be traced back to the ancient crystal ball used for divination and “seeing”. Han Lin et al even used a femtosecond laser to process an ultra-thin flat lens in a two-dimensional single-atom layer with a thickness of only 7 angstroms It has high-quality imaging capabilities, including sub-wavelength resolution and 31% focusing efficiency [4]. Near-field focusing imaging using surface waves has already been applied to a variety of near-field scanning scenes due to its extremely small half-width of the focal peak [6] [7] [8] [9] These lenses are often difficult to process with complex structure, or adapt to flexible design requirements. It will introduce the improvement of the susceptibility function of metalens synthesis under some design requirements, and expand some ideas for metalens design
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