Use of monocrystalline gold flakes for gap plasmon-based metasurfaces operating in the visible

Abstract

Gap plasmon-based optical metasurfaces have been extensively used for demonstration of flat optical elements with various functionalities efficiently operating at near-infrared and telecom wavelengths. Extending their operation to the visible is however impeded by the progressively increased plasmon absorption for shorter wavelengths. We investigate the possibility to improve the performance of gap plasmon-based metasurfaces in the visible by employing monocrystalline gold flakes as substrates instead of evaporated polycrystalline gold films, while using the electron-beam lithography patterning of the evaporated thin gold films for fabrication of top gold nanobricks, which define gap-plasmon resonator elements of the metasurfaces. We demonstrate that the efficiency can be improved by modest but noticeable amount of ≈ 5% if all other configuration parameters are preserved.

Mesoscopic electrodynamics at metal surfaces

“…Crystalline metals are intuitively superior to their polycrystalline counterparts [362], and their practical importance for plasmonics [363] should not be underestimated [287,343,[364][365][366][367][368]. At the same time, it is well-established in surface science [369] that (111) noble-metal surfaces have Shockley states [370] (occasionally also referred to as Tamm states [371]) with a 2DEG, see panel (a) in Figure 16, with no counterparts for other surface facets (or polycrystalline films for that sake).…”

Quantitative near-field characterization of surface plasmon polaritons on monocrystalline gold platelets

“…Here, we perform near-field reflection measurements at visible wavelengths on monocrystalline gold platelets, [25][26][27][28][29][30][31] that have shown to host better plasmonic properties compared to the common polycrystalline gold surfaces. 32,33 We isolate the clearest tip-launched SPPs when illuminating our sample with a laser beam impinging with a low azimuthal angle relative to the edge of the gold platelet.…”

Structural and optical properties of monocrystalline and polycrystalline gold plasmonic nanorods

“…In the case of gold, there are several approaches to chemically reduce typically HAuCl 4 into large monocrystalline microplates in pathways based on aniline [21], two-component ionic liquids [22], ethylene glycol [23,24,25] or tetraoctylammonium bromide (TOABr) [26,27,28] where the latter two are the most prevalent. Although the improvement in optical properties of monocrystalline versus polycrystalline gold is not that radical in bulk [29], it has been shown as a useful platform with improved propagation length of surface plasmons [30] even in complex devices [31,32,33,34]. Additionally, in terms of fabrication of antennas or more complex structures, monocrystalline gold allows fabrication with higher resolution, generally better defined shape and consequently better optical performance [35,36].…”