Mono-crystalline gold platelets: a high-quality platform for surface plasmon polaritons

Abstract

We use mono-crystalline gold platelets with ultra-smooth surfaces and superior plasmonic properties to investigate the formation of interference patterns caused by surface plasmon polaritons (SPPs) with scattering-type scanning near-field microscopy (s-SNOM) at 521 nm and 633 nm. By applying a Fourier analysis approach, we can identify and separate several signal channels related to SPPs launched and scattered by the AFM tip and the edges of the platelet. Especially at the excitation wavelength of 633 nm, we can isolate a region in the center of the platelets where we find only contributions of SPPs which are launched by the tip and reflected at the edges. These signatures are used to determine the SPP wavelength and propagation length. Most importantly, we succeeded in measuring SPP propagation lengths, in terms of power attenuation by 1/e, of 10 µm in excellent agreement with theoretical predictions. Furthermore, we were still able to measure SPP signals after 20 µm propagation, which demonstrates impressively the superior plasmonic quality of these mono-crystalline gold platelets. arXiv:1909.08321v1 [physics.optics]

Ultrafast Electron Tunneling Devices—From Electric‐Field Driven to Optical‐Field Driven

“…Achieving atomically flat metallic interfaces that retain lattice stability has proven particularly challenging to date. [ 64–66 ] Without such ultraprecise surface control, it is believed that further increases in cutoff frequency and power consumption remain limited. This has, in part, driven the search for new materials.…”

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

“…In the past years, s-SNOM has been demonstrated to be a powerful tool to study polaritons of various kinds such as polaritons in two-dimensional (2D) materials 8,9 throughout the optical spectrum, [10][11][12][13][14][15] in anisotropic materials 16,17 and SPPs on metals. [18][19][20] While the characterization of polaritons has been done in many works in the mid-infrared range, [11][12][13][14][15] s-SNOM studies in the visible range are less common. s-SNOM measurements in the visible are indeed more challenging because the smaller extension of the light spot focused onto the atomic force microscope (AFM) tip makes the alignment more difficult and renders less stable scans.…”

“…SPP excitation by the edges is possible in gold since the SPPs have a weak confinement, in contrast to graphene. 11,12,14 In previous works, 19,20 several SPP excitation pathways involving the platelet edge and the tip shaft have been identified. The SPPs excited or scattered at the edge are called edge-launched SPPs, and the ones reflected at the tip shaft are called tip-reflected edge-launched SPPs.…”

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

“…An alternative material platform, which has been receiving increasing attention in the plasmonic community over recent years, is represented by chemically synthesized monocrystalline flakes, also referred to as platelets [34][35][36]. Due to their atomic flatness and well-defined crystal structure, such plasmonic films and nanoparticles exhibit larger plasmon propagation lengths and sharper resonances due to lower Ohmic losses and reduced surface scattering [37,38]. These superior plasmonic properties have been utilized in the fabrication of plasmonic nano-circuits [39,40], nano-antennae [37,41,42], and other structures [43][44][45].…”