Antireflective Multi-Dielectric Metasurfaces Operating in the Visible

As increasingly more demanding photonics applications are brought on-chip, more complex design solutions are employed to deliver enhanced performance: e.g., meta-molecules, inverse-designed freeform structures, and multilayer metasurfaces. Instead, this study introduces anti-reflective metasurfaces fabricated in a single nanolithography step that follows deposition of multiple dielectrics onto a substrate. Anti-reflective metasurfaces offer fundamentally better transmission efficiencies compared to conventional equivalents. Conventional and anti-reflective metalenses, both fabricated in the Ta2O5/SiO2 material platform for 461 nm operation, show an improvement in focusing efficiencies from approximate to 55% to approximate to 90% at low numerical apertures and from approximate to 35% to approximate to 65% at high numerical apertures. Simulations of ideal and imperfect metalenses indicate that anti-reflective metasurfaces not only improve transmission at the design library level, but also reduce spurious diffraction and protect against higher-order scattering. Multi-dielectric metasurfaces that are patterned in a single nanolithography step suppress scattering suffered by their single-dielectric counterparts. Measurements on, and simulations of, SiO2/Ta2O5 anti-reflective metalenses designed for 461 nm showcase how focusing efficiencies can improve from approximate to 55% to approximate to 90% at low numerical apertures and from approximate to 35% to approximate to 65% at high numerical apertures.image

Automated summary

This study introduces a method to fabricate anti-reflective metasurfaces using a single nanolithography step after deposition of multiple dielectrics onto a substrate. Compared to conventional equivalents, anti-reflective metasurfaces offer better transmission efficiencies and reduce spurious diffraction and higher-order scattering. The results show improved focusing efficiencies for both low and high numerical apertures.