Realizing strong light-matter interactions between individual two-level systems and resonating cavities in atomic and solid state systems opens up possibilities to study optical nonlinearities on a single-photon level, which can be useful for future quantum information processing networks. However, these efforts have been hampered by unfavorable experimental conditions, such as cryogenic temperatures and ultrahigh vacuum, required to study such systems and phenomena. Although several attempts to realize strong lightmatter interactions at room temperature using plasmon resonances have been made, successful realizations on the single-nanoparticle level are still lacking. Here, we demonstrate the strong coupling between plasmons confined within a single silver nanoprism and excitons in molecular J aggregates at ambient conditions. Our findings show that deep subwavelength mode volumes V together with quality factors Q that are reasonably high for plasmonic nanostructures result in a strong-coupling figure of merit-Q= ffiffiffi ffi V p as high as ∼6 × 10 3 μm −3=2 , a value comparable to state-of-the-art photonic crystal and microring resonator cavities. This suggests that plasmonic nanocavities, and specifically silver nanoprisms, can be used for room temperature quantum optics. Strong light-matter interactions are not only interesting from a fundamental quantum optics point of view, e.g., for studying entanglement and decoherence, but also because of their relevance for high-end emerging applications such as quantum cryptography [1], quantum networks [2], single-atom lasers [3], ultrafast single-photon switches [4], and quantum information processing [5][6][7]. These phenomena rely on a quantum emitter strongly interacting with a resonant cavity, which leads to cavity and emitter mode hybridization and vacuum Rabi splitting [8]. In the time domain, these strong light-matter interactions manifest themselves as a coherent exchange of energy between the cavity and the emitter occurring on time scales faster than both cavity and emitter dissipative dynamics-a situation that is dramatically different from irreversible spontaneous emission. Traditionally, these quantum optical phenomena have been studied in atomic [9,10] and solid state systems [11][12][13], which are associated with considerable experimental challenges, such as ultrahigh vacuum, cryogenic temperatures, and fabrication issues.A possible solution to these challenges could be to use noble metal nanoparticles instead of photonic crystal and microring resonator cavities [14][15][16][17][18]. This is because metal nanostructures can trap electromagnetic fields on subwavelength scales as so-called surface plasmon excitations. These plasmonic nanocavities possess a number of desirable properties, such as room temperature operation, deep subwavelength mode volumes, and nanoscale dimensions that have been shown to lead to many remarkable phenomena including single-molecule Raman spectroscopy [19][20][21], tip-enhanced imaging [22], ultracompact nanolasers [23], ...
Recent progress in nanophotonics includes demonstrations of meta-materials displaying negative refraction at optical frequencies, directional single photon sources, plasmonic analogies of electromagnetically induced transparency and spectacular Fano resonances. The physics behind these intriguing effects is to a large extent governed by the same single parameter—optical phase. Here we describe a nanophotonic structure built from pairs of closely spaced gold and silver disks that show phase accumulation through material-dependent plasmon resonances. The bimetallic dimers show exotic optical properties, in particular scattering of red and blue light in opposite directions, in spite of being as compact as ∼λ3/100. These spectral and spatial photon-sorting nanodevices can be fabricated on a wafer scale and offer a versatile platform for manipulating optical response through polarization, choice of materials and geometrical parameters, thereby opening possibilities for a wide range of practical applications.
We studied scattering and extinction of individual silver nanorods coupled to the J-aggregate form of the cyanine dye TDBC as a function of plasmon – exciton detuning. The measured single particle spectra exhibited a strongly suppressed scattering and extinction rate at wavelengths corresponding to the J-aggregate absorption band, signaling strong interaction between the localized surface plasmon of the metal core and the exciton of the surrounding molecular shell. In the context of strong coupling theory, the observed “transparency dips” correspond to an average vacuum Rabi splitting of the order of 100 meV, which approaches the plasmon dephasing rate and, thereby, the strong coupling limit for the smallest investigated particles. These findings could pave the way towards ultra-strong light-matter interaction on the nanoscale and active plasmonic devices operating at room temperature.
Warm-white light emitting diodes with high color rendering indices are required for the widespread use of solid state lighting especially indoors. To meet these requirements, we propose and demonstrate warm-white hybrid light sources that incorporate the right color-converting combinations of CdSeZnS core-shell nanocrystals hybridized on InGaNGaN LEDs for high color rendering index. Three sets of proof-of-concept devices are developed to generate high-quality warm-white light with (1) tristimulus coordinates (x,y) = (0.37,0.30), luminous efficacy (LE) =307 lmW, color rending index (CR) =82.4, and correlated color temperature (CCT) =3228 K; (2) (x,y) = (0.38,0.31), LE=323 lmW, CRI=81.0, and CCT=3190 K; and (3) (x,y) = (0.37,0.30), LE=303 lmW, CRI=79.6, and CCT=1982 K. © 2008 American Institute of Physics
Interactions between surface plasmons in metal nanoparticles and electronic excitations in organic chromophores have resulted in many notable findings, including single-molecule Raman scattering, nanoscale lasing, and enhanced fluorescence. Recently, plasmon−exciton interactions have been shown to reach the strong coupling limit, a nonperturbative regime in which a coupled plasmon− exciton system should be treated as a unified hybrid. Strong coupling effects could open up exciting possibilities for manipulating nanoparticle plasmons via molecular degrees of freedom, or vice versa. Optical properties of such hybrid systems can differ drastically from those of noninteracting components. Specifically, optical spectra of a strongly coupled system are expected to exhibit mode splitting due to Rabi oscillations of excitation energy between the system components. However, the interpretation of optical spectra in terms of strong coupling is not a straightforward matter. Here we clarify the nature of plasmon−exciton coupling for the case of rhodamine-6G (R6G) interacting with localized surface plasmons in silver nanodisks using scattering and absorption spectroscopy. We show that this system is only marginally able to reach the strong coupling limit, even for very high molecular concentrations and despite the appearance of obvious mode splitting in scattering. For lower molecular concentrations, the mode splitting we observe should be interpreted as being due to surface-enhanced absorption rather than strong coupling. These results allow us to evaluate the critical concentration necessary for reaching the strong coupling limit and propose conditions for observing strong coupling between single-particle plasmons and organic dyes, such as R6G.
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