Large Hyperpolarizabilities of the Second Harmonic Generation Induced by Nonuniform Optical Near Fields

Yamaguchi, Mas; Nobusada, Katsuyuki

doi:10.1021/acs.jpcc.6b08507

Cited by 17 publications

(14 citation statements)

References 31 publications

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“…From a practical point of view, while the maximum field enhancements are attractive, the sharp fall off of the induced field, due to the small number of electrons, may limit potential plasmonic applications. Fortunately this does lead to extremely large field gradients that could be useful in exciting higher-order multipole excitations [62,63] and nonlinear effects [64,65] …”

Section: B Field Enhancementsmentioning

confidence: 99%

Quantum plasmonic nanoantennas

2017

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We study plasmonic excitations in the limit of few electrons, in one-atom-thick sodium chains. We compare the excitations to classical localized plasmon modes, and we find for the longitudinal mode a quantum-classical transition around 10 atoms. The transverse mode appears at much higher energies than predicted classically for all chain lengths. The electric field enhancement is also considered, which is made possible by considering the effects of electron-phonon coupling on the broadening of the electronic spectra. Large field enhancements are possible on the molecular level allowing us to consider the validity of using molecules as the ultimate small size limit of plasmonic antennas. Additionally, we consider the case of a dimer system of two sodium chains, where the gap can be considered as a picocavity, and we analyze the charge-transfer states and their dependence on the gap size as well as chain size. Our results and methods are useful for understanding and developing ultrasmall, tunable, and novel plasmonic devices that utilize quantum effects that could have applications in quantum optics, quantum metamaterials, cavity-quantum electrodynamics, and controlling chemical reactions, as well as deepening our understanding of localized plasmons in low-dimensional molecular systems.

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Section: B Field Enhancementsmentioning

confidence: 99%

Quantum plasmonic nanoantennas

2017

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“…This result is understandable since the peak at 1.73 eV exhibits a clear plasmon character as illustrated already in Figure . From a practical point of view, the maximum field enhancements are advantageous for photo‐catalytic applications . In this context, the modulations of E fe due to the pyridine attachment are important (Figure , right panel).…”

Section: Resultsmentioning

confidence: 99%

Electric field amplification of plasmon‐molecule hybrids revealed by first‐principles time dependent density functional theory calculations

Muhammed

John

Mokkath

2019

Int J of Quantum Chemistry

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Using first-principles quantum mechanical calculations, we investigate the electric field amplification in hybrid nanostructures composed of few-atom Ni linear chains attached to an organic molecule. We found that the pristine Ni linear chains exhibit localized plasmons and produce nanoscale hotspot regions, acting as a plasmon-like nanoantenna. We demonstrate that localized plasmons provide massive electric field amplification in the vicinity of the molecule. Besides, we also investigated the active modulation of the optical absorption spectra due to the inclusion of a positive and/or negative electric field in the Hamiltonian. We believe that the results presented in this work are important for the emerging field of cavity induced photo-catalysis and will aid in the realization of new quantum nano-optic devices. K E Y W O R D S plasmon-molecule hybrids, polaritons, TD-DFT | INTRODUCTIONComplex nanostructures that combine the dissimilar/complementary properties of its components provide a unique platform for the design and the implementation of novel devices. In this context, polaritonic nanostructures combining resonantly matched localized surface plasmons (LSPs: collective coherent oscillation of conduction electrons driven by electromagnetic fields) and molecular excitons (electron-hole pairs created by the absorption of photons) offer unprecedented opportunities in controlling light on the nanoscale. [1][2][3][4][5][6][7][8][9][10] Understanding the nature and tunability of polaritonic states are important and triggered the development of new applications including chemical sensors, [11] pH meters, [12] and solar cell, [13] to list a few. It is well-known that LSPs can confine the electromagnetic energy to nanometric volumes, below the diffraction limits, which can produce a local enhancement of the external electromagnetic field nearby the nanosystem. When this happens, the system acts as a plasmonic nanoantenna able to amplify local electric fields at the nanoscale. [14][15][16][17][18][19][20][21][22][23][24][25][26] On the other hand, the molecular emitters and/or quantum dots can also be utilized to modify the plasmonic response of a metal nanostructure through a local modification of the dielectric environment. Previous studies [4] have shown that the highly enhanced electric field can mediate plasmon-exciton coupling near the surfaces of plasmonic nanostructures, known as hotspots. The strong and localized field in a plasmonic hot spot enhances the interaction between LSPRs and the excitons, much as it enhances other molecular excitations.The light scattering/absorption properties of metal nanoparticles with specific size, geometry, and composition have been accurately calculated within a classical electrodynamics framework based on Maxwell's equations. [27][28][29][30][31][32] Despite the successful use of this technique to model the optical properties of a vast number of pristine and hybrid metal nano-objects, it is purely classical, and consequently it cannot describe accurately the plexcitonic sta...

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“…Under far-field light irradiation, charges are generated in sub-wavelength objects (nano-scale surface protrusions), resulting in the generation of optical near-fields (ONF), which interact with matter within sub-wavelength distances (such as gas molecules). ONFs have non-uniform electric fields, which can excite dipole-forbidden states of molecules and trigger second harmonic generations 28 . Because the laser photon energy is lower than the O 2 binding energy (5.12 eV), the presence of ONFs is required for the dissociation of O 2 molecules 29 – 33 .…”

Section: Resultsmentioning

confidence: 99%

Improving the electron spin properties of nitrogen-vacancy centres in nanodiamonds by near-field etching

Brandenburg

Nagumo

Saichi

et al. 2018

Sci Rep

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The nitrogen-vacancy (NV) centre in diamond is a promising candidate for quantum computing applications and magnetic sensing applications, because it is an atomic-scale defect with stable coherence time (T2) and reliable accessibility at room temperature. We demonstrated a method for improving the NV spin properties (the full width half maximum (FWHM) value of the magnetic resonance spectrum and T2) through a near-field (NF) etching method under ambient conditions. The NF etching method, based on a He-Cd ultraviolet laser (325 nm), which is longer than the absorption edge of the oxygen molecule, enabled selective removal of defects on the nanodiamond surface. We observed a decrease in the FWHM value close to 15% and an increase in T2 close to 25%. Since our technique can be easily reproduced, a wide range of NV centre applications could be improved, especially magnetic sensing applications. Our results are especially attractive, because they have been obtained under ambient conditions and only require a light source with wavelength slightly above the O2 absorption edge.

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Large Hyperpolarizabilities of the Second Harmonic Generation Induced by Nonuniform Optical Near Fields

Cited by 17 publications

References 31 publications

Quantum plasmonic nanoantennas

Quantum plasmonic nanoantennas

Electric field amplification of plasmon‐molecule hybrids revealed by first‐principles time dependent density functional theory calculations

Improving the electron spin properties of nitrogen-vacancy centres in nanodiamonds by near-field etching

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