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A Tunable Polymer–Metal Based Anti-Reflective Metasurface
Anti-reflective surfaces are of great interest for optical devices, sensing, photovoltaics, and photocatalysis. However, most of the anti-reflective surfaces lack in situ tunability of the extinction with respect to wavelength. This communication demonstrates a tunable anti-reflective surface based on colloidal particles comprising a metal core with an electrochromic polymer shell. Random deposition of these particles on a reflective surface results in a decrease in the reflectance of up to 99.8% at the localized surface plasmon resonance frequency. This narrow band feature can be tuned by varying the pH or by application of an electric potential, resulting in wavelength shifts of up to 30 nm. Electrophoretic particle deposition is shown to be an efficient method for controlling the interparticle distance and thereby further optimizing the overall efficiency of the anti-reflective metasurface. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Nanostructured In3SbTe2 antennas enable switching from sharp dielectric to broad plasmonic resonances
Phase-change materials (PCMs) allow for non-volatile resonance tuning of nanophotonic components. Upon switching, they offer a large dielectric contrast between their amorphous and crystalline phases. The recently introduced “plasmonic PCM” In3SbTe2 (IST) additionally features in its crystalline phase a sign change of its permittivity over a broad infrared spectral range. While optical resonance switching in unpatterned IST thin films has been investigated before, nanostructured IST antennas have not been studied, yet. Here, we present numerical and experimental investigations of nanostructured IST rod and disk antennas. By crystallizing the IST with microsecond laser pulses, we switched individual antennas from narrow dielectric to broad plasmonic resonances. For the rod antennas, we demonstrated a resonance shift of up to 1.2 µm (twice the resonance width), allowing on/off switching of plasmonic resonances with a contrast ratio of 2.7. With the disk antennas, we realized an increase of the resonance width by more than 800% from 0.24 µm to 1.98 µm while keeping the resonance wavelength constant. Further, we demonstrated intermediate switching states by tuning the crystallization depth within the resonators. Our work empowers future design concepts for nanophotonic applications like active spectral filters, tunable absorbers, and switchable flat optics.