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Register a new userAnalysis of the interaction between classical and quantum plasmons via FDTD-TDDFT method
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A powerful hybrid FDTD--TDDFT method is used to study the interaction between classical plasmons of a gold bowtie nanoantenna and quantum plasmons of graphene nanoflakes (GNFs) placed in the narrow gap of the nanoantenna. Due to the hot-spot plasmon of the bowtie nanoantenna, the local-field intensity in the gap increases significantly, so that the optical response of the GNF is dramatically enhanced. To study this interaction between classical and quantum plasmons, we decompose this multiscale and multiphysics system into two computational regions, a classical and a quantum one. In the quantum region, the quantum plasmons of the GNF are studied using the TDDFT method, whereas the FDTD method is used to investigate the classical plasmons of the bowtie nanoantenna. Our analysis shows that in this hybrid system the quantum plasmon response of a molecular-scale GNF can be enhanced by more than two orders of magnitude, when the frequencies of the quantum and classical plasmons are the same. This finding can be particularly useful for applications to molecular sensors and quantum optics.
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In plasmonic chirality, the phenomenon of circular dichroism for achiral nanoparitcles caused by Coulomb interaction between metal nanoparticles (NPs) and chiral molecules have been studied. At the same time, under the resonance condition, the dye molecules and metal NPs will produce huge Rabi splitting due to strong coupling. If the chiral molecules are at the resonance of the plasmon, what will happen for the strong interaction between the plasmon and molecules with chirality introduced? In this paper, we investigate a spherical core-shell model and analyze its spectral phenomena under the excitation of circularly polarized light (CPL). Based on Coulomb interaction between NPs and chiral molecules, we will show how the various factors affect the strong coupling. We have obtained three mechanisms for the interaction between plasmons and chiral molecules: strong coupling (Rabi splitting up to 243mev), enhanced absorption and induced transparency. The interaction between CPL and chiral molecules with the opposite chirality to CPL is stronger than that of the same chirality, and the line width of the two peaks is closer than that of the same chirality, which shows that for the Rabi splitting with chirality, there are deeper mechanisms for the interaction. This result will be helpful for further research on the interaction between plasmon and molecules with chirality.
We study, in the presence of an external electrostatic field, the interatomic interaction between two ground-state atoms coupled with vacuum electromagnetic fluctuations within the dipole coupling approximation based on the perturbation theory. We show that, up to the fourth order, the electrostatic-field-induced interatomic interaction is just the classical dipole-dipole interaction, which disagrees with the recent result from Fiscelli et al. [G. Fiscelli et al., Phys. Rev. Lett. 124, 013604 (2020)]. However, to higher orders, there exist external-field-related quantum corrections to the induced classical electrostatic dipole-dipole interaction. In the sixth order, the external field effectively modifies the atomic polarizability to give rise to a two-photon-exchange quantum correction, while in the eighth order, the external field enables an additional process of three-photon exchange which is not allowed in the absence of the external field, and this process generates an $r^{-11}$ term in the interaction potential in the far regime, where $r$ is the interatomic separation. Numerical estimations show that these external-field-related quantum corrections are much smaller than the two-photon-exchange Casimir-Polder interaction.
From a geometric perspective, the caustic is the most classical description of a wavefunction since its evolution is governed by the Hamilton-Jacobi equation. On the other hand, according to the Madelung-de Broglie-Bohm equations, the most classical description of a solution to the Schrodinger equation is given by the zeros of the Madelung-Bohm potential. In this work, we compare these descriptions and, by analyzing how the rays are organized over the caustic, we find that the wavefunctions with fold caustic are the most classical beams because the zeros of the Madelung-Bohm potential coincide with the caustic. For another type of beams, the Madelung-Bohm potential is in general distinct to zero over the caustic. We have verified these results for the one-dimensional Airy and Pearcey beams, which accordingly to the catastrophe theory, their caustics are stable. Finally, we remark that for certain cases, the zeros of the Madelung-Bohm potential are linked with the superoscillation phenomenon.
Optical non-linearities usually appear for large intensities, but discrete transitions allow for giant non-linearities operating at the single photon level. This has been demonstrated in the last decade for a single optical mode with cold atomic gases, or single two-level systems coupled to light via a tailored photonic environment. Here we demonstrate a two-modes giant non-linearity by using a three-level structure in a single semiconductor quantum dot (QD) embedded in a photonic wire antenna. The large coupling efficiency and the broad operation bandwidth of the photonic wire enable us to have two different laser beams interacting with the QD in order to control the reflectivity of a laser beam with the other one using as few as 10 photons per QD lifetime. We discuss the possibilities offered by this easily integrable system for ultra-low power logical gates and optical quantum gates.
Efficient light-matter interaction lies at the heart of many emerging technologies that seek on-chip integration of solid-state photonic systems. Plasmonic waveguides, which guide the radiation in the form of strongly confined surface plasmon-polariton modes, represent a promising solution to manipulate single photons in coplanar architectures with unprecedented small footprints. Here we demonstrate coupling of the emission from a single quantum emitter to the channel plasmon polaritons supported by a V-groove plasmonic waveguide. Extensive theoretical simulations enable us to determine the position and orientation of the quantum emitter for optimum coupling. Concomitantly with these predictions, we demonstrate experimentally that 42% of a single nitrogen vacancy centre emission efficiently couples into the supported modes of the V-groove. This work paves the way towards practical realization of efficient and long distance transfer of energy for integrated solid-state quantum systems.
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