Self-Arranged Periodic Nanovoids by Ultrafast Laser-Induced Near-Field Enhancement

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.

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Photonic resonator interferometric scattering microscopy

Nature Communications ◽

10.1038/s41467-021-21999-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Nantao Li ◽

Taylor D. Canady ◽

Qinglan Huang ◽

Xing Wang ◽

Glenn A. Fried ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Scattered Light ◽

Near Field ◽

Field Enhancement ◽

Protein Detection ◽

Significant Loss ◽

Photonic Band Structure ◽

Large Intensity ◽

Photonic Band ◽

Intensity Contrast

AbstractInterferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the <1% transmitted light to create a large intensity contrast. Importantly, the scattered photons assume the wavevectors delineated by PC’s photonic band structure, resulting in the ability to utilize a non-immersion objective without significant loss at illumination density as low as 25 W cm−2. An analytical model of the scattering process is discussed, followed by demonstration of virus and protein detection. The results showcase the promise of nanophotonic surfaces in the development of resonance-enhanced interferometric microscopies.

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Ultrahigh electric and magnetic near field enhancement based on high-Q whispering gallery modes in subwavelength all-dielectric resonators

Applied Physics Express ◽

10.35848/1882-0786/ac10a8 ◽

2021 ◽

Author(s):

Xiao-Jing Du ◽

Zhong-Jian Yang ◽

Ma-Long Hu ◽

Lin Ma ◽

Jun He

Keyword(s):

Near Field ◽

Field Enhancement ◽

Whispering Gallery Modes ◽

Dielectric Resonators ◽

High Q ◽

Whispering Gallery

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electromagnetic field at the particl e has to be computed numerically. An example of such a computation using a program based on [49] is given in Fig. 4. But not only doe s the Mie theory describe an enhancement of the laser intensity in the particles' near field, it also predicts that for certain values of the size parameter nd/X (d denoting the particle diameter, À the laser wavelength) the enhancement should be particularly efficient, resulting in a resonant intensity enhancement, the so-called "Mie-resonances". 3.2.2. Near-field induced substrate damage When inspecting contaminated samples by scanning electron microscopy (SEM) or atomic force microscopy (AFM ) after DLC using ns laser pulses, the consequences of the field enhancement process became obvious: all over the cleaned areas w e found substrate damages localized exactly at the former particle positions [35, 37-39]. These damages manifested as melting pools or even holes in the surface, typical examples can be seen in Fig. 5. The consequences for the laser cleaning process are obvious. The intensity enhancement reduces the maximum laser fluence that can be applied in the process. Usually in laser cleaning studies [19, 31 ] the laser fluence corresponding to the melting threshold of a bare surface is taken as the damage threshold fluence. Our experiments show clearly that this is an inadequate definition. Instead one must take into account the enhanced laser fluence underneath the particles, as it will be discussed in Section 4. Fro m the obtained AFM images we were able to analyse in detail the surface profile at the damaged sites. Here we found that for high field enhancement factors the silicon substrate was not only molten , but that some material was even ablated (see Sec. 4). The momentum transfer to the particles during the ablation process significantly contributes to the cleanin g process and hence local substrate ablation

Surface Contamination and Cleaning ◽

10.1201/9789047403289-48 ◽

2003 ◽

pp. 327-330

Keyword(s):

Laser Fluence ◽

Near Field ◽

Particle Diameter ◽

Surface Profile ◽

Field Enhancement ◽

Damage Threshold ◽

Laser Pulses ◽

Laser Wavelength ◽

Laser Cleaning ◽

Intensity Enhancement

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Plasmonic interference modulation for broadband nanofocusing

Nanophotonics ◽

10.1515/nanoph-2021-0405 ◽

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.

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Dye-doped spheres with plasmonic semi-shells: Lasing modes and scattering at realistic gain levels

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.4.110 ◽

2013 ◽

Vol 4 ◽

pp. 974-987 ◽

Cited By ~ 16

Author(s):

Nikita Arnold ◽

Boyang Ding ◽

Calin Hrelescu ◽

Thomas A Klar

Keyword(s):

Cross Section ◽

Near Field ◽

Field Enhancement ◽

Higher Order ◽

Silver Layer ◽

Far Field ◽

Spectral Features ◽

Polystyrene Spheres ◽

Higher Order Modes ◽

Lasing Modes

We numerically simulate the compensation of absorption, the near-field enhancement as well as the differential far-field scattering cross section for dye-doped polystyrene spheres (radius 195 nm), which are half-covered by a silver layer of 10–40 nm thickness. Such silver capped spheres are interesting candidates for nanoplasmonic lasers, so-called spasers. We find that spasing requires gain levels less than 3.7 times higher than those in commercially available dye-doped spheres. However, commercially available concentrations are already apt to achieve negative absorption, and to narrow and enhance scattering by higher order modes. Narrowing of the plasmonic modes by gain also makes visible higher order modes, which are normally obscured by the broad spectral features of the lower order modes. We further show that the angular distribution of the far-field scattering of the spasing modes is by no means dipole-like and is very sensitive to the geometry of the structure.

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Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.9.215 ◽

2018 ◽

Vol 9 ◽

pp. 2306-2314 ◽

Cited By ~ 23

Author(s):

Valerio F Gili ◽

Lavinia Ghirardini ◽

Davide Rocco ◽

Giuseppe Marino ◽

Ivan Favero ◽

...

Keyword(s):

Frequency Conversion ◽

Near Infrared ◽

Strong Field ◽

Second Harmonic ◽

Near Field ◽

Field Enhancement ◽

High Refractive Index ◽

Plasmonic Nanostructures ◽

Ohmic Losses ◽

Order Of Magnitude

Background: Dielectric nanoantennas have recently emerged as an alternative solution to plasmonics for nonlinear light manipulation at the nanoscale, thanks to the magnetic and electric resonances, the strong nonlinearities, and the low ohmic losses characterizing high refractive-index materials in the visible/near-infrared (NIR) region of the spectrum. In this frame, AlGaAs nanoantennas demonstrated to be extremely efficient sources of second harmonic radiation. In particular, the nonlinear polarization of an optical system pumped at the anapole mode can be potentially boosted, due to both the strong dip in the scattering spectrum and the near-field enhancement, which are characteristic of this mode. Plasmonic nanostructures, on the other hand, remain the most promising solution to achieve strong local field confinement, especially in the NIR, where metals such as gold display relatively low losses. Results: We present a nonlinear hybrid antenna based on an AlGaAs nanopillar surrounded by a gold ring, which merges in a single platform the strong field confinement typically produced by plasmonic antennas with the high nonlinearity and low loss characteristics of dielectric nanoantennas. This platform allows enhancing the coupling of light to the nanopillar at coincidence with the anapole mode, hence boosting both second- and third-harmonic generation conversion efficiencies. More than one order of magnitude enhancement factors are measured for both processes with respect to the isolated structure. Conclusion: The present results reveal the possibility to achieve tuneable metamixers and higher resolution in nonlinear sensing and spectroscopy, by means of improved both pump coupling and emission efficiency due to the excitation of the anapole mode enhanced by the plasmonic nanoantenna.

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