Axicon metalens for broadband light harvesting

In this study, an axicon metalens comprising a large central disc surrounded by nanoposts for energy harvesting in composite metal-oxide semiconductor sensors was designed, fabricated, and experimentally characterized. The main role of the central disc is focusing light; the nanoposts of various diameters deflect light to form a Bessel-like beam. The spatial distribution of the optical transmission was measured using micro-hyperspectral imaging. The axicon metalens concentrates the light to the sensitive area of the sensor and also harvests light from adjacent pixels. After adding an axicon metalens, the normalized peak transmission is up to 250% at lambda = 700 nm as compared to a blank TiO2 film. The experimental results had fair agreement with the finite-difference-time-domain simulation. The ultra-broadband energy-harvesting performance of the sensor suggests that it could be applied in surveillance and Internet of Things applications.

Automated summary

This study presents the design, fabrication, and experimental characterization of an axicon metalens for energy harvesting in composite metal-oxide semiconductor sensors. The metalens consists of a central disc for light focusing and nanoposts for deflecting light to form a Bessel-like beam. Micro-hyperspectral imaging is used to measure the spatial distribution of optical transmission. The axicon metalens improves the peak transmission by up to 250% compared to a blank TiO2 film, and its performance is validated by finite-difference-time-domain simulation.