Plasmonic Elliptical Nanohole Arrays for Chiral Absorption and Emission in the Near-Infrared and Visible Range

Abstract

Chiral plasmonic nanostructures with tunable handedness-dependent absorption in the visible and infrared offer chiro-optical control at the nanoscale. Moreover, coupling them with emitting layers could lead to chiral nanosources, important for nanophotonic circuits. Here, we propose plasmonic elliptical nanohole arrays (ENHA) for circularly dependent near-infrared and visible emission. We first investigate broadband chiral behavior in an Au-ENHA embedded in glass by exciting it with plane waves. We then study the coupling of ENHA with a thin emitting layer embedded in glass; we focus on the emission wavelengths which provided high chirality in plane-wave simulations. Our novel simulation set-up monitors the chirality of the far-field emission by properly averaging a large set of homogeneously distributed, randomly oriented quantum sources. The intrinsic chirality of ENHA influences the circular polarization degree of the emitting layer. Finally, we study the emission dependence on the field distribution at the excitation wavelength. We demonstrate the chiral absorption and emission properties for Au-ENHA emitting in the near-infrared range, and for Ag-ENHA which is excited in green range and emits in the Lumogen Red range. The simple geometry of ENHA can be fabricated with low-cost nanosphere lithography and be covered with emission gel. We thus believe that this design can be of great importance for tunable chiral nanosources.

Fluorescence Spectroscopy of Enantiomeric Amide Compounds Enforced by Chiral Light

“…As previously stated, chiral detection at much lower concentrations is needed in the industry, and the authors in [31] managed to detect enantiomer concentrations down to zeptomole levels by coupling them with the resonant nanostructured materials and monitoring the transmission changes in the near-infrared range. Here, our molecules were designed to emit in the green range, which overlaps with resonances of plasmonic nanostructures such as nanohole arrays [29,30,32]. In future work, we will cover plasmonic nanostructures with the presented solutions and measure both FDCD and passive extinction changes.…”

“…We specifically design chiral compounds to exhibit circular dichroism in the ultraviolet range and emit in the visible green range. The choice of this design is due to two reasons; firstly, proof-of-concept FDCD measurements of new solutions are experimentally easier in the visible range, and, secondly, we were led by the recent reports of chirality in nanostructured substrates in the visible range [29,30], which have potential for coupling with emitting molecules in future. The synthesis is based on affordable starting compounds, mild reactions, and easy purification, which result in two pure enantiomeric compounds R-FA1 and S-FA1.…”

Broadband, angle-dependent optical characterization of asymmetric self-assembled nanohole arrays in silver

“…Next, we perform the rst optimization to lower the polarization ratio minimum; we use the ENHA analysis from ref. (Petronijevic et al 2020b;Petronijevic et al 2021b), where absorption CD of ENHA was studied in detail. In those works, ENHA showed strong chiral behavior when diameters scaled as , and , while the tilt angle was kept at , and the metal thickness was 100 nm.…”

Characterization of Chirality in Diffractive Metasurfaces by Photothermal Deflection Technique

“…The sample was based on an hexagonal array of polystyrene nanospheres; the periodicity of the array and the diameter of the nanospheres were 522 nm, and 370 nm, respectively, and the metasurface lay on a 1 mm glass substrate. The tilted Ag deposition defined the asymmetric Ag shell, as well as the elliptical nanohole array (ENHA) [38] on the substrate. The geometry of such a metasurface led to diffraction orders for the wavelengths below its periodicity.…”