Metasurface optical characterization using quadriwave lateral shearing interferometry

TL;DR

This paper demonstrates the use of quadriwave lateral shearing interferometry (QLSI) for precise, full optical characterization of various metasurfaces, enabling better design and understanding of these ultrathin optical components.

Contribution

It introduces QLSI as a versatile, high-resolution technique for characterizing the phase profiles of different metasurfaces, surpassing traditional intensity-based methods.

Findings

QLSI can measure local phase with high sensitivity.

Effective for various metasurface types, including metalenses and deflectors.

Provides detailed optical characterization to improve metasurface design.

Abstract

An optical metasurface consists of a dense and usually non-uniform layer of scattering nanostructures behaving as a continuous and extremely thin optical component, with predefined phase and intensity transmission/reflection profiles. To date, various sorts of metasurfaces (metallic, dielectric, Huygens-like, Pancharatman-Berry, etc.) have been introduced to design ultrathin lenses, beam deflectors, holograms, or polarizing interfaces. Their actual efficiencies depend on the ability to predict their optical properties and to fabricate non-uniform assemblies of billions of nanoscale structures on macroscopic surfaces. To further help improve the design of metasurfaces, precise and versatile post-characterization techniques need to be developed. Today, most of the techniques used to characterize metasurfaces rely on light intensity measurements. Here, we demonstrate how quadriwave lateral shearing interferometry (QLSI), a quantitative phase microscopy technique, can easily achieve full optical characterization of metasurfaces of any kind, as it can probe the local phase imparted by a metasurface with high sensitivity and spatial resolution. As a means to illustrate the versatility of this technique, we present measurements on two types of metasurfaces, namely Pancharatnam-Berry and effective-refractive-index metasurfaces, and present results on uniform metasurfaces, metalenses and deflectors.