The functionality of most of the metasurfaces that have been investigated so far, especially in illuminations with arbitrarily linearly polarized incident light, are restricted to x- or y-polarized incoming light. In particular, filtering out one of the two orthogonal polarizations of the incoming electromagnetic wave loses the incident light energy and limits the potential performance of the metasurface. In this study, by utilizing the cross-shaped silicon metaatoms that support the simultaneous excitation of electric and magnetic dipoles under the illumination of both x- and y- orthogonal polarizations, we overcome the polarization-restricted functionality of the metalenses. By selecting the metaatoms arrangement in the metalens structure, which follows the hyperbolic phase profiles for both x- and y-polarized incoming light waves at the same time, we obtain the light intensity distribution with the extended depth of focus (EDOF) or enhanced intensities at the focal spot with the focusing efficiency 65% for the numerical aperture of 0.7. Utilizing metaatoms with the ability to control the two orthogonal incoming polarizations develops a new methodology for using the full potential and intensity of the arbitrary polarized incoming light. The present design concept of metaatoms has several advantages that are not limited to metalenses alone but can be applied in all metasurfaces realized to have good efficiency. Finally, the proposed metalenses are suitable for imaging, optical tweezers and lithography applications, where subwavelength light intensity distributions with EDOF are the most desirable property.
Optical metasurfaces with versatile focal properties have great importance and adaptability in photonic systems and potential applications. The unique capability of the ultracompact device in forming and modulating light fields is triggered to configure multifocal setups. This study introduces a geometric metasurface consisting of dielectric cross-shaped metaatoms with a suitable phase profile operating in the visible regime that can transport the conjugate focal spot of the auto-focused Airy beam (AFAB) into real space by adding the proper convex lens profile and resulting in three foci whose positions and intensities can be adjusted without redesigning metaatoms architecture. The cross-shaped meta-atoms with complete control of the amplitude and phase of the incident light have considered diverse functionalities for the x-and y-components of the incident light, generating six focal spots with high adjustable intensities shown in free space. The proposed hybrid metalens has shown robustness against change in geometrical design while controlling multifocal setups, which can be useful in developing polarization-sensitive devices, photonics, medicine, micromachining and imaging applications to realize beneficial results.
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