Reflective metalens with an enhanced off-axis focusing performance

Opt Express. 2022 Sep 12;30(19):34117-34128. doi: 10.1364/OE.468316.

Abstract

Metalenses are one of the most promising metasurface applications. However, all-dielectric reflective metalenses are rarely studied, especially regarding their off-axis focusing performance. After experimentally studying the material optical properties in this work, we propose reflective metalens based on titanium dioxide (TiO2) and silicon dioxide (SiO2), which operate at a visible wavelength of 0.633 µm. Unlike conventional reflective metalenses based on metallic mirrors, the proposed device was designed based on a modified parabolic phase profile and was integrated onto a dielectric distributed Bragg reflector periodic structure to achieve high reflectivity with five dielectric pairs. The focusing efficiency characteristics of the metalens were experimentally studied for beam angles of incidence between 0 and 30. The results reveal that the focusing efficiency for the modified metalens design remains higher than 54%, which is higher than 50%, making it promising for photonic miniaturization and integration.