Modification of Fluorescence Properties in Single Colloidal Quantum Dots by Coupling to Plasmonic Gap Modes

Yuan, Chi‐Tsu; Wang, Y. C.; Cheng, Hui-Wen; Wang, H. S.; Kuo, Mark Yen‐Ping; Shih, Min‐Hsiung; Tang, Jau

doi:10.1021/jp401993r

Cited by 41 publications

(58 citation statements)

References 34 publications

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“…Because this enables a planar fabrication technique, the gaps in patch antennas can be controlled with nanometre 25 and sub-nanometre 26 precision. To date, however, micrometre-scale plasmonic patch antennas have shown only modest emission rate enhancements (∼80) and low radiative QE 23,27 .In this Letter we demonstrate a nanoscale patch antenna (NPA) that has large emission rate enhancement, high radiative efficiency, directionality of emission, and deep sub-wavelength dimensions. The NPA consists of a colloidally synthesized silver nanocube (side length of ∼80 nm) situated over a metal film, separated by a well-controlled nanoscale gap (5-15 nm) embedded with emitters ( Fig.…”

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confidence: 88%

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Probing the mechanisms of large Purcell enhancement in plasmonic nanoantennas

et al. 2014

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To move nanophotonic devices such as lasers and single-photon sources into the practical realm, a challenging list of requirements must be met, including directional emission 1-5 , room-temperature and broadband operation 6-9 , high radiative quantum efficiency 1,4 and a large spontaneous emission rate 7 . To achieve these features simultaneously, a platform is needed for which the various decay channels of embedded emitters can be fully understood and controlled. Here, we show that all these device requirements can be satisfied by a film-coupled metal nanocube system with emitters embedded in the dielectric gap region. Fluorescence lifetime measurements on ensembles of emitters reveal spontaneous emission rate enhancements exceeding 1,000 while maintaining high quantum efficiency (>0.5) and directional emission (84% collection efficiency). Using angle-resolved fluorescence measurements, we independently determine the orientations of emission dipoles in the nanoscale gap. Incorporating this information with the threedimensional spatial distribution of dipoles into full-wave simulations predicts time-resolved emission in excellent agreement with experiments.Typical luminescent emitters have relatively long emission lifetimes (∼10 ns) and non-directional emission. Unfortunately, these intrinsic optical properties are poorly matched to the requirements of nanophotonic devices. For example, in single-photon sources, fast radiative rates are required for operation at high frequencies, and directionality is needed to achieve a high collection efficiency 10 . In addition, with plasmonic lasers, enhanced spontaneous emission into the cavity mode can reduce the lasing threshold 9 . As a result, much work has focused on modifying the photonic environment of emitters to enhance 11 the spontaneous emission rate, known as the Purcell effect 12 . Early approaches concentrated on integrating emitters into dielectric optical microcavities and showed modest emission rate enhancements [13][14][15] . However, dielectric cavities require high quality factors for large rate enhancements, which makes these cavities mismatched with the spectrally wide emission from inhomogeneously broadened or room-temperature emitters. Plasmonic nanostructures are a natural solution to the spectral mismatch problem because of their relatively broad optical resonances and high field enhancements [16][17][18] . Despite these advantages and the capability for emission rate enhancement 19 , many plasmonic structures suffer from unacceptably high non-radiative decay due to intrinsic losses in the metal, or have low directionality of emission 7 . In plasmonic structures, the Purcell factor (defined as the fractional increase in total emission rate) has contributions from an increased radiative rate and from an increased non-radiative rate due to metal losses. It is therefore critical to specify the fraction of energy emitted as radiation, known as the radiative quantum efficiency (QE). From knowledge of the Purcell factor and the QE, the enhancement in the ...

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Probing the mechanisms of large Purcell enhancement in plasmonic nanoantennas

et al. 2014

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“…[3][4] The enhanced field resulting from surface plasmon resonance has been utilized for surface enhancing spectroscopy such as surface-enhanced Raman scattering (SERS), [5][6][7] refractive index monitoring, [8][9][10] and manipulation of light-matter interaction. [11][12][13][14][15][16][17][18][19][20] In addition to intrinsic properties of constituent metals, the optical features of plasmonic structures usually depend on their morphology. Therefore, considerable efforts have been devoted to developing fabrication/synthesis methods [21][22][23][24][25][26][27] to obtain new single structures with the desired optical properties.…”

Section: Introductionmentioning

confidence: 99%

High Order Gap Modes of Film-Coupled Nanospheres

Huang

Chen

2015

J. Phys. Chem. C

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Tailoring coupled plasmonic structures is an alternative way to obtain new optical properties of plasmonic materials. Recently, film-coupled nanoparticle systems with high stability and controllability have been used to probe the ultimate limits of field enhancement/confinement and near-field interaction with other quantum emitters. When the gap between particles and films is below a few nanometers, induced high order (HO) gap modes become significant. In this report, we investigate these HO modes associated with the system of a gold nanosphere positioned above a gold film, separated by a nanometer scale spacer layer.The shift in far-field scattering profile under different excitation conditions and collection wavelengths indicates the influence of HO modes and the results are compared to the corresponding simulations. In addition, the far-field scattering spectra/patterns by multipole expansion and the near-field distributions by FEM, both calculated with dielectric function of the low damping factor are utilized to resolve the individual HO modes. These findings not only identify the HO gap modes but also clarify their excitation conditions and far-field/near-field scattered field distribution. The effect of HO modes should be taken into account when the interaction between the gap field and quantum emitters nearby is investigated for active plasmonic devices.

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“…This process increases the rates of their spontaneous of emission (Purcell effect), allowing them to compete better with the non-radiative decay processes. [18][19][20] In such techniques, which are referred in the following as "normal" plasmonic, the inherent issues associated with the surface defects remain unresolved.…”

Section: Introductionmentioning

confidence: 99%

Functional Metal-oxide Plasmonic Metastructures: Ultrabright Semiconductor Quantum Dots with Polarized Spontaneous Emission and Suppressed Auger Recombination

et al. 2019

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We use localized surface plasmon resonances in metallic nanoantennas to suppress defect environment of colloidal quantum dots and to enhance and polarize their spontaneous emission. For this we study the interaction of such quantum dots with functional metal-oxide plasmonic metastructures consisting of an Au/Si Schottky junction in close vicinity of a Si/Al oxide charge barrier. We show that optically excited quantum dots can couple with such metastructures via their electric dipole fields, offering super-plasmonic processes that include the impact of hot electron generation and fixed negative charges at the Si/Al oxide junction. For metallic nanoantennas with small aspect ratios our results show that these metastructures can reduce the defect-induced nonradiative decay rates of quantum dots such that their lifetime can become significantly longer than those in the absence of such nanoantennas. For metallic nanoantennas with larger aspect ratios these structures lead to ultrahigh enhancement of exciton-plasmon coupling, making the spontaneous emission of quantum dots strongly polarized while increasing their emission intensities by about 50 times. These results show by keeping excitons in the cores of quantum dots, the metastructures suppress migration of photo-excited electrons to surface defects and, therefore, reduce Auger recombination. Coherent dynamics associated with the quantum dot-induced exciton-plasmon coupling is theoretically investigated.

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Modification of Fluorescence Properties in Single Colloidal Quantum Dots by Coupling to Plasmonic Gap Modes

Cited by 41 publications

References 34 publications

Probing the mechanisms of large Purcell enhancement in plasmonic nanoantennas

Probing the mechanisms of large Purcell enhancement in plasmonic nanoantennas

High Order Gap Modes of Film-Coupled Nanospheres

Functional Metal-oxide Plasmonic Metastructures: Ultrabright Semiconductor Quantum Dots with Polarized Spontaneous Emission and Suppressed Auger Recombination

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