Programming Metasurface Near‐Fields for Nano‐Optical Sensing

• Published in: Advanced optical materials 2021-08, Vol.9 (15), p.n/a
• Main Authors: Buijs, Robin D., Wolterink, Tom A.W., Gerini, Giampiero, Verhagen, Ewold, Koenderink, A. Femius
• Format: Article
• Language: English
• Subjects: Far fields; Illumination; Materials science; Metasurfaces; nanoantennas; near‐field enhancement; Numerical analysis; Optics; plasmonic nanostructures; Spatial resolution
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202100435

Control of optical fields at the nanoscale holds the promise of fast, efficient imaging methods, but is elusive due to the diffraction limit. This paper investigates how a single metasurface patch in the near field of a sample plane may be used to create a wide variety of intensity patterns by applying different illumination profiles from the far field. Numerical analysis shows that one metasurface patch may be used to generate complete bases of illumination patterns on a grid as fine as λ/16. The limits of control are explored in terms of degrees of freedom on the illumination side and spatial resolution on the sample side. These illumination patterns are expected to enable sub‐wavelength structured illumination microscopies, compressive imaging and sensing. Quantitative analysis of how the engineered fields may be used for detection of small scattering particles demonstrates the potential the approach holds for nanoscale optical sensing. Diffraction precludes full field control from the far‐field, but no such restriction applies to metasurface near‐fields. In this paper, the authors engineer illuminating wavefronts to dynamically shape the near‐field of a metasurface patch, achieving full bases of exposure patterns in a sample plane, at deeply sub‐diffractive resolution. Calculations show these patterns can be used for efficient scatterometric nanoparticle sensing.