Conformal Talbot-effect-focusing performance of nested gallium-doped zinc oxide nanorings at communication wavelength

Abstract

Metasurfaces, artificial micro- and nano-photonic structures can modify wavefront of electromagnetic waves to the desired form. Metalenses are the metasurfaces assuming the role of focusing light. The focusing performance of nested gallium-doped zinc oxide nanoring-arrangements functionalized by conformal Talbot effect is investigated for communication wavelength 1550 nm. The Talbot-effect-focusing performance of the 2D finite-sized structures are computationally demonstrated in a systematically manner. The impact of geometrical parameters on the primary focal spot and focusing performance parameters such as numerical aperture, full-width half-maximum, focal depth, efficiency, and fill-factor is examined and summarized via finite difference time-domain numerical simulations. All samples presenting an alternative plasmonic option in this work yield a good focusing efficiency of >50%, absolute efficiency of >19%, numerical aperture up to 0.67, focal depth up to 1.4 times of focal length, and a wide focal spot size up to 6.0654 times of operating wavelength. As a result of finite-sized construction, conformal Talbot effect is examined from a novel alternative plasmonics perspective. Thus, a new planarized focusing platform is employed by using a nanostructured microlens, acting conformal transformation optics devices with low-cost and light capturing tolerance.