Flexibly tunable surface plasmon resonance by strong mode coupling using a random metal nanohemisphere on mirror

Abstract

<jats:title>Abstract</jats:title><jats:p>We propose a unique random metal nanohemisphere on mirror (NHoM) structure to tune the surface plasmon (SP) resonance in a flexible manner. The SP resonance peak was split into two peaks owing to the strong coupling between the SP mode in the metal nanohemisphere and the mirror image mode generated in the metal substrate. This phenomenon is based on the fact that the strong coupling and the induced electromagnetic effects are similar to those pertaining to the Rabi splitting, Fano resonance, and electromagnetically induced transparency, thus providing quantum effect analogies. These phenomena have recently attracted increased attention and have been studied with nanocavities fabricated with top-down nanotechnologies. Compared with previous reports, NHoM structures can be fabricated in a much easier manner and are tunable in rather wider wavelength regions without nanofabrication technologies. The SP resonance peaks were enhanced, sharpened dramatically, and tuned flexibly, based on the optimization of the thickness of the spacer layer between the metal hemisphere and metal substrate. Experimental results were reproduced and were explained based on finite difference time domain (FDTD) simulations. These phenomena have never been observed previously on similar nanosphere on mirror (NSoM) because nanohemispherical structures were required. The NHoM nanocavity structure has a quality factor &gt;200 that is surprisingly high for the localized SP mode of nanoparticles. Flexible tuning of the SP resonance with the use of NHoM is envisaged to lead to the development of new applications and technologies in the field of plasmonics and nanophotonics.</jats:p>

Water-Wettable Open Plasmonic Nanocavities for Ultrasensitive Molecular Detections in Multiple Phases

“…Because of the strong confinement of the optical field, the coupling between the charge oscillations in a metal nanoparticle and the image charges in a nearby mirror film has attracted considerable attention in numerous applications ranging from metamaterials to photocatalysis to plasmonic sensing. − To date, to create a tiny cavity between the metal nanoparticle and metal film, it is essential to have a spacer layer that separates them in proximity. For example, nonmetal thin layers of either SiO 2 , semiconductors, or self-assembled monolayers are deposited onto a gold film, and thereafter, gold nanoparticles are placed on top of the nonmetal layer. − Alternatively, gold nanoparticles fully coated with either SiO 2 or organic molecules can be introduced onto a gold film. − In either case, the nanocavities are produced as occupied by the spacer layers. Consequently, it is evident that the molecules in surrounding media are unable to diffuse into the nanocavity, where the optical field is significantly enhanced.…”

Localized surface plasmon resonance in deep ultraviolet region below 200 nm using a nanohemisphere on mirror structure

“…Figure 3b shows the spatial distribution of the localized electric field around the NHoM structure at the peak wavelengths (158 and 393 nm). The two peaks of the NHoM structure were the modes owing to the mirror image charges of the metal substrate 27 . The electrical fields of the excitation were included in E x as the background because the excitation pulse was x-polarized.…”

Fabrication of perfect plasmonic absorbers for blue and near-ultraviolet lights using double-layer wire-grid structures

“…Such filters can be divided into three types: filters that transmit light of a specific wavelength, filters that reflect light, and filters that absorb light. Examples include filters used for biosensing [1], infrared spectroscopy [2], solar cells [3][4][5], cooling by heat release [6][7][8], image sensors [9], color filters [10][11][12][13][14][15][16][17][18], detectors [19][20][21], and fluorescence observations [22].…”