scholarly journals Distinguishable Plasmonic Nanoparticle and Gap Mode Properties in a Silver Nanoparticle on a Gold Film System Using Three-Dimensional FDTD Simulations

Nanomaterials ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 582 ◽  
Author(s):  
Vasanthan Devaraj ◽  
Jong-Min Lee ◽  
Jin-Woo Oh
Keyword(s):  
Layer Thickness ◽  
Silver Nanoparticle ◽  
Dielectric Layer ◽  
Gold Film ◽  
Computational Study ◽  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Plasmonic Nanoparticle ◽  
Gap Mode

We present a computational study of the near-field enhancement properties from a plasmonic nanomaterial based on a silver nanoparticle on a gold film. Our simulation studies show a clear distinguishability between nanoparticle mode and gap mode as a function of dielectric layer thickness. The observed nanoparticle mode is independent of dielectric layer thickness, and hence its related plasmonic properties can be investigated clearly by having a minimum of ~10-nm-thick dielectric layer on a metallic film. In case of the gap mode, the presence of minimal dielectric layer thickness is crucial (~≤4 nm), as deterioration starts rapidly thereafter. The proposed simple tunable gap-based particle on film design might open interesting studies in the field of plasmonics, extreme light confinement, sensing, and source enhancement of an emitter.

Simulation of Electromagnetic Field Distribution at a Nanowire Probe for Near Field Scanning Optical Microscopy

2008 ◽  
Author(s):  
Nathan P. Malcolm ◽  
Alex J. Heltzel ◽  
Li Shi ◽  
John R. Howell
Keyword(s):  
Optical Microscopy ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Fdtd Simulation ◽  
Plasmonic Nanoparticle ◽  
Excitation Laser ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

This work studies a new design of a near field scanning optical microscopy (NSOM) probe based on a ZnO nanowire sub-wavelength waveguide terminated with a plasmonic gold nanoparticle. Three-dimensional finite difference time domain (FDTD) simulation is used to visualize light guiding in the nanowire and near field coupling between the plasmonic nanoparticle and the substrate. The simulation results reveal local field enhancement at the gap between the nanoparticle and a gold substrate when the nanowire axis is tilted from the substrate normal by a small angle. The enhancement occurs only along the cross section plane that is parallel to the polarization of the excitation laser beam. The regime of field enhancement is much smaller than the diameter of the 100 nm plasmonic particle, making the nanowire probe well suited for NSOM with superior spatial resolution and signal to noise ratio compared to the state of the art.

scholarly journals Effects of gap thickness and emitter location on the photoluminescence enhancement of monolayer MoS2 in a plasmonic nanoparticle-film coupled system

Nanophotonics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 2097-2105
Author(s):  
Xiaozhuo Qi ◽  
Tsz Wing Lo ◽  
Di Liu ◽  
Lantian Feng ◽  
Yang Chen ◽  
...  
Keyword(s):  
Near Field ◽  
Central Area ◽  
Field Enhancement ◽  
Coupled System ◽  
Film Structure ◽  
Plasmonic Nanoparticle ◽  
Emitter Location ◽  
Radiation Properties ◽  
Radiation Enhancement ◽  
Quantum Emitters

AbstractPlasmonic nanocavities comprised of metal film-coupled nanoparticles have emerged as a versatile nanophotonic platform benefiting from their ultrasmall mode volume and large Purcell factors. In the weak-coupling regime, the particle-film gap thickness affects the photoluminescence (PL) of quantum emitters sandwiched therein. Here, we investigated the Purcell effect-enhanced PL of monolayer MoS2 inserted in the gap of a gold nanoparticle (AuNP)–alumina (Al2O3)–gold film (Au Film) structure. Under confocal illumination by a 532 nm CW laser, we observed a 7-fold PL peak intensity enhancement for the cavity-sandwiched MoS2 at an optimal Al2O3 thickness of 5 nm, corresponding to a local PL enhancement of ∼350 by normalizing the actual illumination area to the cavity’s effective near-field enhancement area. Full-wave simulations reveal a counterintuitive fact that radiation enhancement comes from the non-central area of the cavity rather than the cavity center. By scanning an electric dipole across the nanocavity, we obtained an average radiation enhancement factor of about 65 for an Al2O3 spacer thickness of 4 nm, agreeing well with the experimental thickness and indicating further PL enhancement optimization. Our results indicate the importance of configuration optimization, emitter location and excitation condition when using such plasmonic nanocavities to modulate the radiation properties of quantum emitters.

scholarly journals Plasmonic interference modulation for broadband nanofocusing

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shaobo Li ◽  
Shuming Yang ◽  
Fei Wang ◽  
Qiang Liu ◽  
Biyao Cheng ◽  
...  
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Incident Beam ◽  
Plasmonic Mode ◽  
Resonant Structures ◽  
Interference Modulation ◽  
Near Field Imaging ◽  
Linearly Polarized ◽  
Radially Polarized

Abstract Metallic plasmonic probes have been successfully applied in near-field imaging, nanolithography, and Raman enhanced spectroscopy because of their ability to squeeze light into nanoscale and provide significant electric field enhancement. Most of these probes rely on nanometric alignment of incident beam and resonant structures with limited spectral bandwidth. This paper proposes and experimentally demonstrates an asymmetric fiber tip for broadband interference nanofocusing within its full optical wavelengths (500–800 nm) at the nanotip with 10 nm apex. The asymmetric geometry consisting of two semicircular slits rotates plasmonic polarization and converts the linearly polarized plasmonic mode to the radially polarized plasmonic mode when the linearly polarized beam couples to the optical fiber. The three-dimensional plasmonic modulation induces circumference interference and nanofocus of surface plasmons, which is significantly different from the nanofocusing through plasmon propagation and plasmon evolution. The plasmonic interference modulation provides fundamental insights into the plasmon engineering and has important applications in plasmon nanophotonic technologies.

scholarly journals On the formation of the counter-rotating vortex pair in transverse jets

2001 ◽  
Vol 446 ◽  
pp. 347-373 ◽  
Author(s):  
L. CORTELEZZI ◽  
A. R. KARAGOZIAN
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Transverse Jets ◽  
Vortical Structures ◽  
Jet In Crossflow ◽  
Dynamical Generation ◽  
Counter Rotating Vortex Pair

Among the important physical phenomena associated with the jet in crossflow is the formation and evolution of vortical structures in the flow field, in particular the counter-rotating vortex pair (CVP) associated with the jet cross-section. The present computational study focuses on the mechanisms for the dynamical generation and evolution of these vortical structures. Transient numerical simulations of the flow field are performed using three-dimensional vortex elements. Vortex ring rollup, interactions, tilting, and folding are observed in the near field, consistent with the ideas described in the experimental work of Kelso, Lim & Perry (1996), for example. The time-averaged effect of these jet shear layer vortices, even over a single period of their evolution, is seen to result in initiation of the CVP. Further insight into the topology of the flow field, the formation of wake vortices, the entrainment of crossflow, and the effect of upstream boundary layer thickness is also provided in this study.

Effect of Substrate and Nanoparticle Spacing on Plasmonic Enhancement in Three-Dimensional Nanoparticle Structures

2017 ◽  
Vol 5 (4) ◽  
Author(s):  
Anil Yuksel ◽  
Edward T. Yu ◽  
Jayathi Murthy ◽  
Michael Cullinan
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Polarized Light ◽  
Field Enhancement ◽  
Transverse Magnetic ◽  
Plasmonic Enhancement ◽  
Nanoparticle Assemblies ◽  
Nanoparticle Interactions ◽  
Gap Spacing ◽  
532 Nm

Surface plasmon polaritons associated with light-nanoparticle interactions can result in dramatic enhancement of electromagnetic fields near and in the gaps between the particles, which can have a large effect on the sintering of these nanoparticles. For example, the plasmonic field enhancement within nanoparticle assemblies is affected by the particle size, spacing, interlayer distance, and light source properties. Computational analysis of plasmonic effects in three-dimensional (3D) nanoparticle packings are presented herein using 532 nm plane wave light. This analysis provides insight into the particle interactions both within and between adjacent layers for multilayer nanoparticle packings. Electric field enhancements up to 400-fold for transverse magnetic (TM) or X-polarized light and 26-fold for transverse electric (TE) or Y-polarized light are observed. It is observed that the thermo-optical properties of the nanoparticle packings change nonlinearly between 0 and 10 nm gap spacing due to the strong and nonlocal near-field interaction between the particles for TM polarized light, but this relationship is linear for TE polarized light. These studies help provide a foundation for understanding micro/nanoscale heating and heat transport for Cu nanoparticle packings under 532 nm light under different polarization for the photonic sintering of nanoparticle assemblies.

scholarly journals Engineering Efficient Self-Assembled Plasmonic Nanostructures by Configuring Metallic Nanoparticle’s Morphology

2021 ◽  
Vol 22 (19) ◽  
pp. 10595
Author(s):  
Vasanthan Devaraj ◽  
Jong-Min Lee ◽  
Ye-Ji Kim ◽  
Hyuk Jeong ◽  
Jin-Woo Oh
Keyword(s):  
Near Field ◽  
Simplified Model ◽  
Plasmonic Nanostructures ◽  
Dipole Mode ◽  
Plasmonic Nanoparticle ◽  
Mode Characteristics ◽  
Cluster A ◽  
Self Assembled ◽  
Nanoparticle Cluster ◽  
Gap Mode

We reveal the significance of plasmonic nanoparticle’s (NP) shape and its surface morphology en route to an efficient self-assembled plasmonic nanoparticle cluster. A simplified model is simulated in the form of free-space dimer and trimer nanostructures (NPs in the shape of a sphere, cube, and disk). A ~200% to ~125% rise in near-field strength (gap mode enhancement) is observed for spherical NPs in comparison with cubical NPs (from 2 nm to 8 nm gap sizes). Full-width three-quarter maximum reveals better broad-spectral optical performance in a range of ~100 nm (dimer) and ~170 nm (trimer) from spherical NPs as compared to a cube (~60 nm for dimer and trimer). These excellent properties for sphere-based nanostructures are merited from its dipole mode characteristics.

scholarly journals Modifying Plasmonic-Field Enhancement and Resonance Characteristics of Spherical Nanoparticles on Metallic Film: Effects of Faceting Spherical Nanoparticle Morphology

Coatings ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 387 ◽  
Author(s):  
Vasanthan Devaraj ◽  
Hyuk Jeong ◽  
Chuntae Kim ◽  
Jong-Min Lee ◽  
Jin-Woo Oh
Keyword(s):  
Near Infrared ◽  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Device Fabrication ◽  
Metallic Film ◽  
Linear Optics ◽  
Cross Sectional ◽  
Non Linear Optics ◽  
Surface Enhanced

A three-dimensional finite-difference time-domain study of the plasmonic structure of nanoparticles on metallic film (NPOM) is presented in this work. An introduction to nanoparticle (NP) faceting in the NPOM structure produced a variety of complex transverse cavity modes, which were labeled S11 to S13. We observed that the dominant S11 mode resonance could be tuned to the desired wavelength within a broadband range of ~800 nm, with a maximum resonance up to ~1.42 µm, as a function of NP facet width. Despite being tuned at the broad spectral range, the S11 mode demonstrated minimal decrease in its near field enhancement characteristics, which can be advantageous for surface-enhanced spectroscopy applications and device fabrication perspectives. The identification of mode order was interpreted using cross-sectional electric field profiles and three-dimensional surface charge mapping. We realized larger local field enhancement in the order of ~109, even for smaller NP diameters of 50 nm, as function of the NP faceting effect. The number of radial modes were dependent upon the combination of NP diameter and faceting length. We hope that, by exploring the sub-wavelength complex optical properties of the plasmonic structures of NPOM, a variety of exciting applications will be revealed in the fields of sensors, non-linear optics, device engineering/processing, broadband tunable plasmonic devices, near-infrared plasmonics, and surface-enhanced spectroscopy.

scholarly journals Understanding the Role of Different Substrate Geometries for Achieving Optimum Tip-Enhanced Raman Scattering Sensitivity

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 376
Author(s):  
Lu He ◽  
Mahfujur Rahaman ◽  
Teresa I. Madeira ◽  
Dietrich R.T. Zahn
Keyword(s):  
Spatial Resolution ◽  
Near Field ◽  
Field Enhancement ◽  
Combined System ◽  
Gold Thin Film ◽  
Gold Nanostructure ◽  
Tip Enhanced Raman Spectroscopy ◽  
Metal Tip ◽  
20 Nm ◽  
Gap Mode

Tip-enhanced Raman spectroscopy (TERS) has experienced tremendous progress over the last two decades. Despite detecting single molecules and achieving sub-nanometer spatial resolution, attaining high TERS sensitivity is still a challenging task due to low reproducibility of tip fabrication, especially regarding very sharp tip apices. Here, we present an approach for achieving strong TERS sensitivity via a systematic study of the near-field enhancement properties in the so-called gap-mode TERS configurations using the combination of finite element method (FEM) simulations and TERS experiments. In the simulation study, a gold tip apex is fixed at 80 nm of diameter, and the substrate consists of 20 nm high gold nanodiscs with diameter varying from 5 nm to 120 nm placed on a flat extended gold substrate. The local electric field distributions are computed in the spectral range from 500 nm to 800 nm with the tip placed both at the center and the edge of the gold nanostructure. The model is then compared with the typical gap-mode TERS configuration, in which a tip of varying diameter from 2 nm to 160 nm is placed in the proximity of a gold thin film. Our simulations show that the tip-nanodisc combined system provides much improved TERS sensitivity compared to the conventional gap-mode TERS configuration. We find that for the same tip diameter, the spatial resolution achieved in the tip-nanodisc model is much better than that observed in the conventional gap-mode TERS, which requires a very sharp metal tip to achieve the same spatial resolution on an extended metal substrate. Finally, TERS experiments are conducted on gold nanodisc arrays using home-built gold tips to validate our simulation results. Our simulations provide a guide for designing and realization of both high-spatial resolution and strong TERS intensity in future TERS experiments.

scholarly journals Designing an Efficient Self-Assembled Plasmonic Nanostructures from Spherical Shaped Nanoparticles

2021 ◽  
Author(s):  
Vasanthan Devaraj ◽  
Jong-Min Lee ◽  
Ye-ji Kim ◽  
Hyuk Jeong ◽  
Jin-Woo Oh
Keyword(s):  
Near Field ◽  
Simplified Model ◽  
Plasmonic Nanostructures ◽  
Dipole Mode ◽  
Plasmonic Nanoparticle ◽  
Mode Characteristics ◽  
Cluster A ◽  
Self Assembled ◽  
Nanoparticle Cluster ◽  
Gap Mode

We reveal the significance of plasmonic nanoparticle’s (NP) shape and its surface morphology en route to an efficient self-assembled plasmonic nanoparticle cluster. A simplified model is simulated in the form of free-space dimer and trimer nanostructures (NPs in shape of sphere, cube, and disk). A ~ 200 % to ~ 125% raise in near field strength (gap mode enhancement) is observed for spherical NPs in comparison with cubical NPs (from 2 nm to 8 nm gap sizes). Full-width three-quarter maximum reveals better broad-spectral optical performance in a range of ~ 100 nm (dimer) and ~ 170 nm (trimer) from spherical NPs as compared to a cube (~ 60 nm for dimer and trimer). These excellent properties for sphere-based nanostructures are merited from its dipole mode characteristics.

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