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Polarization oscillations map the resonant modes of antennas of increasing length.(a) Confocal luminescence microscopy images of arrays of identical antennas of increasing length. The colour code reflects the DOLP of the emission of QDs coupled to nanowires of different lengths, including resonant modes j. The polarization along the long antenna axis decreases with antenna mode and oscillates on and off resonance with length due to a varying coupling efficiency. (b) Statistics taken over ~200 antennas per length. Vertical grey lines indicate the s.d. around the average polarization. Red dots show the most frequent polarization. Green squares identify the individual antennas presented in Figs 3 and 4. (c) Linear polarization of antenna emission predicted by the 1D resonator model, which describes only pure antenna emission, neglecting radiation that did not couple to the antenna mode. The DOLP (red line) is close to unity irrespective of length, even after taking into account the effect of the confocal imaging system on polarization detection. This model reproduces the oscillations in polarization with a fit to the average (blue line in b). We add the polarization of pure antenna modes, which would correspond to 100% QD–antenna coupling, and a background of uncoupled emission in both linear polarizations.
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Multipolar transitions other than electric dipoles are generally too weak to be observed at optical frequencies in single quantum emitters. For example, fluorescent molecules and quantum dots have dimensions much smaller than the wavelength of light and therefore emit predominantly as electric dipoles. Here we demonstrate controlled emission of a q...
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... 60 to 900 nm. The emission is detected in two polarization channels, parallel and perpendicular to the long axis of the wires, with signals I 8 and I > , respectively. The polarization of the emission depends on the mode of the antenna, evolving from linear polarization along the antenna to unpolarized emission for increasing order resonances (Fig. 2a). For quantitative analysis, we define the degree of linear ...
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... By taking statistics over B200 antennas per length, we observe clear oscillations in polarization degree as a function of antenna length due to the evolution on and off resonance (Fig. 2b). Yet, linearly polarized emission along the antenna, with DOLPE1, is expected for an oscillating current on a line and predicted by our resonator model even off resonance (Fig. 2c). The observed oscillations in polarization in Fig. 2b are due to partial coupling of the QDs to the antennas, namely, a fraction of the emission does not ...
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... over B200 antennas per length, we observe clear oscillations in polarization degree as a function of antenna length due to the evolution on and off resonance (Fig. 2b). Yet, linearly polarized emission along the antenna, with DOLPE1, is expected for an oscillating current on a line and predicted by our resonator model even off resonance (Fig. 2c). The observed oscillations in polarization in Fig. 2b are due to partial coupling of the QDs to the antennas, namely, a fraction of the emission does not interact with the antenna mode. The relative weight of the contributions of the polarized antenna mode and an unpolarized, uncoupled background varies as the antenna is tuned to ...
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... oscillations in polarization degree as a function of antenna length due to the evolution on and off resonance (Fig. 2b). Yet, linearly polarized emission along the antenna, with DOLPE1, is expected for an oscillating current on a line and predicted by our resonator model even off resonance (Fig. 2c). The observed oscillations in polarization in Fig. 2b are due to partial coupling of the QDs to the antennas, namely, a fraction of the emission does not interact with the antenna mode. The relative weight of the contributions of the polarized antenna mode and an unpolarized, uncoupled background varies as the antenna is tuned to resonance with the QD emission. The background comprises ...
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... . The resonances in polarization are thus attributed to the resonant modes j, and indicate the best overlap between antenna mode and the QD luminescence spectrum, centred around 800 nm. After taking into account this partial coupling of QDs to the antenna mode, our model reproduces the observed oscillations in average polarization with a fit (Fig. 2b, blue line) based on a superposition of the theoretical antenna emission plus an incoherent sum of two perpendicular polarizations describing uncoupled emission. The average polarization decreases for increasing order of modes because the resonances are damped due to dissipation, resulting in a lower coupling efficiency. This average ...
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... are damped due to dissipation, resulting in a lower coupling efficiency. This average represents the inhomogeneously broadened distribution of antennas in the arrays, similarly to the broadened spectrum of an ensemble of molecules. Individual antennas exhibiting higher degrees of polarization are singled out from this ensemble (squares in Fig. 2b). We focus next on these cases where the emitter-antenna coupling is ...
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... from what is expected in free space ( Supplementary Fig. S1). Fourier images of single antennas contain the directions of emission of the coupled system into the substrate. For off-resonance lengths, similar to the absence of polarization, the QD angular emission is hardly affected by the antenna and the pattern is rotationally symmetric ( Fig. 3a and Supplementary Fig. S2). At resonance, the angular pattern becomes dominated by the antenna mode. For the j ¼ 1 resonance, the emission represents a linear dipole along the antenna (Fig. 3c); the degeneracy in transition dipole moment of our QDs (Fig. 3a) is lifted by coupling to the antenna mode 6 . The j ¼ 2 resonance has even charge symmetry and its ...
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... Having direct access to the radiation pattern of emitternanoantenna systems helped to further expand the directional control of light emission through the design of more complex antennas supporting multipolar resonances [75], [81]. In tailored split-ring resonators (SRRs), the scattering patterns of electric dipole, magnetic dipole, and electric quadrupole resonances interfere in the far-field to produce highly directional emission in a large bandwidth. ...
... (d) Directional emission of quantum dots coupled to half-wave and Yagi-Uda antennas [74]. (e) Split-ring resonators (SRRs) supporting multipolar resonances, which interfere in the far-field, hence, producing highly directional emission in a large bandwidth, as measured in the Fourier space [75]. (f) GaAs nanopillar supporting a bound state in the continuum (BIC) at normal incidence [76]. ...
Standard optical characterization and spectroscopy techniques rely on the measurement of specular reflection, transmission, or emission at normal incidence. Although the usefulness of these methods is without question, they do not provide information on the angular dependence of the scattered light and, therefore, miss crucial insights on the physical processes governing light emission and scattering. In this Review, we explain the basics of Fourier imaging and show how it can be used to measure the angular distribution of scattered light in single-shot measurements. We then give a comprehensive panorama on recent research exploiting this technique to analyze nanostructures and detail how it unlocks fundamental understandings on the underlying physics of nanophotonic structures. We finally describe how simple additions to a Fourier imaging setup enable measuring not only the radiation pattern of an object but also the energy, polarization, and phase toward resolving all aspects of light in real time.
... However, their position and shape can be determined by placing oscillating dipoles close to an isolated nanoring. These dipoles can excite the dark modes, leading to an increased power emission of the dipoles at their resonance positions [36,37]. Monitoring the power that is emitted by these dipoles gives direct information about the dark modes (see Supplement 1 Fig. ...
In this paper we investigate the Fano resonances of a ring-disc nanostructure that consists of two nanodiscs and two concentric nanorings. The dark modes of both nanorings can couple to the bright mode of the nanodiscs, leading to separate Fano resonances from the outer and the inner nanoring. The concentric arrangement of the two nanorings allows for a coupling between the dark modes of the outer and the inner nanoring, thus creating an additional interaction that influences the Fano resonances of the dual-ring nanostructure. This interaction is investigated by comparing the Fano resonances of the complete dual-ring structure with the isolated Fano resonances of the individual single-ring structures. The effect of the coupling between dark modes on the Fano resonances is verified using a model of coupled harmonic oscillators that describe the Fano resonances of this system in a classical analogy. Lastly we compare the sensitivity of a single-ring nanostructure with that of a dual-ring nanostructure to investigate the effects of a coupling between dark modes on the sensing performance.
... The coupling of plasmonic and excitonic modes launches plasmon-exciton polaritons, triggering a wealth of optical phenomena [16,[52][53][54]. Excitons in an emitter can generate surface plasmons via energy transfer to the adjacent plasmonic nanostructures. ...
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... Related meta-applications modeled with the multipolar approach have been quite varied. They include active optical MTMs [103], quantum emitters coupled with nanowire optical antennas [104], and nonlinear responses of optical metastructures [105]- [107], ...
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