Abstract

In order to realize the function of subdiffraction focusing using a single flat lens, a special metalens is proposed to modulate the circularly polarized light. Initially, the analyses indicate that the phase shift can cover [$0,2\pi$] by changing the rotation angle of a quadrangular-frustum pyramid-shaped structure from 0° to 180°, while the average amplitude transmittance can reach 96% at the wavelength of $\lambda =1550\mathrm{nm}$. Then, a flat metalens is designed by carefully arranging the quadrangular-frustum pyramid-shaped structures. The simulated results show that a focal spot could be obtained at the focal length of about $f=2.87\lambda$, and the focusing efficiency is $\sim 14.9\%$. Meanwhile, the full width at half maximum (FWHM) of the focusing spot is only $0.48\lambda$, which is smaller than the diffraction limit. Furthermore, this designed metalens can function comparatively with a conventional lens in one-to-one imaging.

© 2019 Optical Society of America

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