Efficient arbitrary polarized light focusing by silicon cross-shaped metaatoms

Abstract

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.

Robust Design of Autofocused Airy Beam-Based Multifocal Metalens With Tunable Intensities

“…For producing the AFAB-based metalens with six focal spots, the selected metaatoms of Figure 3 are arranged along the x-direction by PBC in the ydirection. The one hundred metaatoms are considered for designing the metalens, and they are selected among 23000 metaatoms that are swept over the geometric parameters of metaatoms to full phase cover of 0 to 2π [33]. For the metalens design that consists of silicon cross-shaped metaatoms covered on the silica substrate, we used silicon (Si) with a high relative permittivity of 13.5 and silica (SiO2) with a permittivity of 2.1 and refractive indices of silica and silicon are chosen from [34].…”

“…By partially modifying the amplitude and setting the central part equal to 0.5, the focal spot of the lens is also presented, and the combination of AFAB and metalens leads to three real focal spots. Simultaneous excitation of electric and magnetic dipoles in these cross-shaped metaatoms, separately for x and ycomponents of the electric field of the incident light, and therefore, the possibility of full control of the transmitted light phase and amplitude through them is shown in our previously published paper [33].…”