Theoretical Study of Terahertz Near-Field Enhancement Assisted by Shape Resonance in Rectangular Hole Arrays in Metal Films

Terahertz antennas can greatly enhance the near fields and enable strong light–matter interactions, and thus have been widely used in applications such as terahertz sensing and detection. Here we propose a novel approach to further enhance the near fields in terahertz antennas. We show that by sandwiching hyperbolic metamaterials that are composed of InSb and SiO 2 multilayer and that are dressed with hole arrays, between a terahertz dipole antenna and the substrate, the near-field electric field intensities in the antenna can be further enhanced by more than three times. Simulations reveal that this enhancement originates from the doubly enhanced in-plane electric field component and the significantly enhanced out-of-plane electric field component. We expect this work will advance the design of terahertz antennas that are widely used in sensors and detectors.

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Abnormal Fano Profile in Graphene-Wrapped Dielectric Particle Dimer

Photonics ◽

10.3390/photonics7040124 ◽

2020 ◽

Vol 7 (4) ◽

pp. 124

Author(s):

Yang Huang ◽

Pujuan Ma ◽

Ya Min Wu

Keyword(s):

Energy Level ◽

Theoretical Study ◽

Dipole Moments ◽

Near Field ◽

Field Enhancement ◽

Plasmon Hybridization ◽

Far Field ◽

Wave Polarization ◽

Fermi Energy Level ◽

Field Spectrum

We give a theoretical study on the near field enhancement and far field spectrum of an adjacent graphene-wrapped sphere dimer with different radii. The Fano profile is found in the near field enhancement spectrum of such a symmetry-broken dimer system, which is, however, hidden in the far field spectrum. We demonstrate that this kind of Fano profile is rising from the coupling of dimer’s plasmon hybridization modes by analyzing the dipole moments of each sphere. Moreover, different orientation of incident wave polarization will lead to the different plasmon hybridization coupling, thus giving rise to a different Fano profile. By changing the Fermi energy level, we could achieve tunable Fano profile in near field enhancement.

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

Nanophotonics ◽

10.1515/nanoph-2020-0178 ◽

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.

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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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