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We report recent research progress on the strong coupling between an ensemble of quantum emitters (QEs) or chiral molecules and plasmon in the nanoparticle cluster, including strong interaction between chiral molecules and orbital angular momentum of photon, multi-qubit entanglement for two-level QEs, resonant energy transfer and so on.
We have proposed a metal disc-shaped terahertz surface wave splitter with a center hole and radially placed gratings. Unfortunately, appreciable reflected waves have been observed from the input port of the center hole. To reduce the reflected waves, we insert a metal rod with a tapered end into the center hole of the disc-shaped splitter operating at two frequencies. It is found that the reflected...
In this study, we observe that a dark mode is not necessarily prerequisite for an asymmetric Fano resonance to take place in plasmonic structures. The characteristic asymmetry feature of Fano resonance is retained in a plasmonic structure when both superradiant and subradiant oscillators are externally driven. Double Fano resonances are experimentally and theoretically observed where a common subradiant...
We propose a hybrid cavity-channel structure to tune optical wavelengths using narrow-band resonances. High spectral selectivity and high angular dependency of the absorptance are reported due to the resonance between propagating surface plasmon modes and channel modes. By varying the incident angle, we could adjust both the position and the amplitude of the reflectance dips thus achieving highly...
In this talk, we will overview nonlinear plasmonic effects due to intrinsic, hydrodynamic metal nonlinearity, enhanced by sub-wavelength field confinement, interaction between plasmonic resonances and nonlocal effects. In particular, various nonlinear effects, such as nonlinear mode coupling, high-order harmonics and coherent supercontinuum generation will be discussed.
For many years, the (quantum) theory of light in condensed matter has been focused on describing classical and quantum phenomena on scales larger than the wavelength and regarded the material in which light propagates, is absorbed or emitted from in terms of effective parameters such as a refractive index. Recent progress in transformation optics and nanophotonics and metamaterials physics, however,...
We present a theoretical description of the electromagnetic coupling between a two-level system and the localized modes supported by the most paradigmatic plasmonic cavity: a pair of metallic spheres separated by a nanometric gap. Our method exploits the invariance of Maxwell's Equations under geometric transformations to obtain analytical expressions for the spectral density evaluated in the surroundings...
Terahertz (THz) spectroscopy is a promising way to measure the spectrum of low-frequency modes of molecules or ensembles, such as crystals and polymers, including proteins. However, the main drawback of THz spectroscopy is its extremely low sensitivity. In the present study, we report on signal enhancement in THz spectroscopy achieved by depositing a mino acid molecules or their derivatives on a gold...
Transient absorption spectroscopy has been extensively used in recent years to examine the temporal response of isolated nanoparticles (NPs) to the absorption of light [1]. These studies are largely based on the use of the surface plasmon resonance (SPR) to monitor characteristics of the NP such as electronic and lattice temperature, shape and morphology as a function of time. In the case of extended...
Nano antennas have been proved to be a good platform to tune the emission properties of a localized source, e.g., an electric dipole [1]. Besides the enhancement of the emission efficiency, it is also feasible to control the radiating directivity of a dipole by utilizing the plasmon modes of these antennas. Here we show that both the forward and backward unidirectional radiation can be realized by...
The interaction between the excitonic J-band of J-aggregate molecules and localized plasmonic resonances supported by metallic structures can be large enough to reach the regime of strong coupling, giving rise to two hybridized modes [1, 2]. The new hybrid system is often characterized in extinction measurements, where the strong coupling results in an avoided crossing of the two modes as the detuning...
In quantum physics it is well known that the spin of a particle can determine its motion: this is known as spin-orbit interaction. It is not so well known that Maxwell's equations can show the same effect with electromagnetic radiation. Contrary to the approximate assumptions of ray optics, in which rays propagate independently of light polarization, Maxwell's equations tell us that the spin of photons...
Using atomically flat gold surfaces, we observe long- and short-range surfaces plasmons on unstructured as well as patterned surfaces. Time-resolved two-photon photoemission microscopy reveals the rich dynamics of plasmon propagation, including spin-orbit coupling in surface plasmons with orbital angular momentum up to l = 20.
Highly doped graphene has been demonstrated to be a promising plasmonic material where the excitation of surface plasmons can significantly enhance the interaction with light [1, 2]. Here we investigate the coupling effects in graphene nanodisk oligomers (heptamer) [2] and try to employ one of the interesting phenomena from the coupling, the so called Fano-resonances, for sensing applications [3]...
Graphene appears to be a good candidate in designing tunable devices operating in THz spectral ranges owing to its tunability of conductivity. It can be tuned dynamically via electrostatic doping [1, 2]. Here we propose a tunable terahertz half wave plate based on the hybridization effect caused by coupling interactions between plasmonic resonances in the two coupled graphene nanodisks (CGN). We show...
Recently, an elegant transformation-optics approach has been used to describe the optical properties of metal nanoparticles separated by nanometric gaps [1]. In this talk, we further develop this quasi-analytical methodology by applying it to the investigation of the electromagnetic interaction between a single quantum emitter and the localized modes supported by these plasmonic cavities. We will...
Surface plasmon-polaritons are a possible solution for on-chip transportation and manipulation of information. Although there are several possibilities for designing the plasmonic waveguides, the two major caveats for all of them are the coupling to/from external sources and the losses they exhibit.
Plasmonics have shown convincing evidence as critical tool for the development of advanced functional nanomaterials and devices. In the Polymer Nanohybrid Materials at Ewha Womans University, a comprehensive approach for the exploitation of plasmonic nanostructures has been systematically performed to seek their potential applications as key elements in diverse optoelectronic devices. We actively...
We discuss our recent experimental and theoretical works on the efficient generation of prominent and robust Fano resonances in 3D metamaterials (MMs). The 3D MMs are formed by integrating vertical U-shape SRRs or vertical rectangular plates along a planar metallic hole array with extraordinary optical transmission (EOT) built by means of homemade focused ion-beam (FIB) lithography [1, 2]. In such...
A T-shape plasmonic structure, consisting of a stub resonator coupled with bus waveguide and cavity, has been investigated numerically and theoretically. Due to the near-field coupling mechanism between bright and dark modes, plasmon induced transparency can be observed in transmission spectrum. Moreover, it is demonstrated theoretically that the first order resonance mode can exist or not in the...
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