Abstract
Dielectric metasurfaces based on amorphous silicon (a-Si) nanodisks are interesting for nanophotonic applications due to the high refractive index and mature/low temperature fabrication of a-Si. The investigated metasurfaces consist of a-Si nanodisk arrays embedded in a transparent film. The diameter-dependent optical properties of the nanodisk Mie resonators have been investigated by finite-difference time-domain (FDTD) simulations and spectrally-resolved reflectivity and transmission measurements. Well-ordered substrate-free a-Si nanodisk arrays were fabricated and characterized with regard to their broadband anti-reflection properties when placed on a crystalline silicon (c-Si) surface, and reflectivity/ transmission properties when embedded in a polydimethylsiloxane (PDMS) film. Our results confirm broadband anti-reflection when placed on silicon, while the optical characteristics of the nanodisks embedded in PDMS are shown to be potentially useful for color/NIR filter applications as well as for coloring on the micro/nanoscale.
Highlights
Metasurfaces composed of dielectric nanostructures (in the order of λair/(2·nsc); where λair is the wavelength of light in air and nsc is the refractive index (RI) of the dielectric) working as Mie resonators and optical antennas have received much attention due to their unique optical properties for absorption enhancement and engineering light scattering [1,2,3,4,5,6]
Dielectric metasurfaces based on amorphous silicon (a-Si) nanodisks are interesting for nanophotonic applications due to the high refractive index and mature/low temperature fabrication of a-Si
Well-ordered substratefree a-Si nanodisk arrays were fabricated and characterized with regard to their broadband anti-reflection properties when placed on a crystalline silicon (c-Si) surface, and reflectivity/ transmission properties when embedded in a polydimethylsiloxane (PDMS) film
Summary
Metasurfaces composed of dielectric nanostructures (in the order of λair/(2·nsc); where λair is the wavelength of light in air and nsc is the refractive index (RI) of the dielectric) working as Mie resonators and optical antennas have received much attention due to their unique optical properties for absorption enhancement and engineering light scattering [1,2,3,4,5,6]. Plasma-enhanced chemical vapor deposition (PECVD) of a-Si(:H) is possible at temperatures between 30 and 300 °C, which makes this low temperature processing available for substrate materials like glass, plastics and metals This paves the way for integration of nanodisk-based metasurfaces in a broader scope of material combinations than has been reported. On the other hand, when they are placed on/embedded in a low RI (transparent) medium (e.g., SiO2 or polydimethylsiloxane (PDMS)), coloring in the reflectance mode can be obtained, determined by the geometrical properties of the nanodisks and their array period. The dimension range of the nanodisks used in this work was chosen due to their ability to support multi-modes; this in order to use the relative spectral location of the occurring Mie resonances for transmission (optical) filter applications. The main focus of this work is on the transmittance properties of the a-Si nanodisk arrays embedded in PDMS with regard to possible optical filter applications
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