Polarization-insensitive metalens with high efficiency for optical fiber communication

Metamaterials (MMs) are artificially crafted materials that demonstrate extraordinary electromagnetic properties that not observable in naturally occurring materials. The permittivity and permeability of metamaterial is dependent on its subwavelength periodic structures thus can be changed by carefully engineering the periodic structure. etc,allowing us to control or shape the wavefronts of Electromagnetic (EM) waves and offer novel functionalities like Bessel Beam generation, lensing, Holography, and cloaking. The application of metalens in optical fiber with high transmission, in particular, is a prominent topic in optics and photonics these days because spot size in optical fibers is limited by diffraction. This study focuses on designing dielectric metalenses with high transmission efficiency in the Ultraviolet (UV) and visible regime for multiple wavelengths $(\lambda=370\mathrm{n}\mathrm{m},\lambda=480\mathrm{n}\mathrm{m},\lambda=532\mathrm{n}\mathrm{m},\lambda=633\mathrm{n}\mathrm{m})$. The periodic nanostructure elements of the metasurfaces are made from gallium nitride - a low loss dielectric material with a high refractive index whereas Silicon Dioxide (SiO2) is employed as a substrate layer. In this research we present polarization-insensitive UV-Vis dielectric metalenses with full $(0-2\pi)$ phase coverage in the ultraviolet and visible regime. The proposed metalenses employ cylindrical-shaped nano-pillars unit elements. The individual unit elements can attain a transmission efficiency of 95% and overall lens transmission efficiency as high as 48%. This study paves the way for multidimensional regime nanophotonic platforms based on flat optical elements, enabling a range of applications such as lithography, imaging, spectroscopy, and lensing with good efficiency.