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Tip-enhanced strong coupling spectroscopy, imaging, and control of a single quantum emitter

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Science Advances  12 Jul 2019:
Vol. 5, no. 7, eaav5931
DOI: 10.1126/sciadv.aav5931
  • Fig. 1 TESC spectroscopy and energy diagram for the plasmon and exciton in the weak and strong coupling regime.

    (A) The strongly confined ∣Ez∣ fields in a single isolated QD (CdSe/ZnS) with a 0.5-nm dielectric capping layer (Al2O3) and a tilted Au tip induce coupling between the plasmon and exciton. Simulated out-of-plane (B) and in-plane (C) optical field distributions in the plasmonic cavity shown in (A). a.u., arbitrary units. (D) Energy diagram for the plasmonic cavity (red), QD (blue), and upper and lower polariton states (green) with PL energy in the weak (orange) and strong (green) coupling regimes. When the coupling exceeds system losses, the split polariton states emerge and the system begins to undergo Rabi splittings and Rabi oscillations, as illustrated above.

  • Fig. 2 Tip-enhanced plexciton PL at room temperature in the strong coupling regime.

    (A) PL spectra of the gap plasmon (red), QD exciton (blue), the weakly coupled plasmon-exciton mode (orange), and the strongly coupled plexciton mode (green). (B) PL evolution of the uncoupled (top) and the strongly coupled (bottom) single QD. (C) TEPL spectra for a polarization parallel (green) and perpendicular (red) with respect to the tip. (D) FEM simulation of scattering spectra for the plasmonic cavity without QD (red) and with a single QD (green). In (A), (C), and (D), the dots and lines indicate the measurement (or simulation) data and the corresponding model fits, respectively.

  • Fig. 3 TESC spectra with increasing coupling strength and plexciton energy diagram with QD detuning.

    (A) TEPL spectra of different single QDs with variation in coupling strength g and Rabi frequency. (B) Polariton energies from model fits (circles) and anticrossing curves from model calculations (lines) for each of the measured TEPL spectra of 21 different QDs. The expected surface plasmon (red) and QD (blue) detuning dependence is obtained from averaged values from the modeled 21 spectra.

  • Fig. 4 Active control of tip-induced single QD strong coupling.

    TEPL spectra as the lateral (A) and vertical (B) tip-QD distances are varied from 30 to 0 nm and from 0 to 4 nm, respectively. (C and D) Coupling strength g and Rabi frequency Ω derived from model fit of the distance-dependent TEPL spectra from (A) and (B).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/7/eaav5931/DC1

    Section S1. Characterization of single isolated QDs

    Section S2. Lorentzian fitting of emission spectra of uncoupled QD and cavity

    Section S3. A coupled oscillator model for plexciton spectra

    Section S4. Parameters of model fit

    Section S5. FEM simulation of strong coupling

    Section S6. FDTD simulation of optical field distribution in a plasmonic cavity

    Fig. S1. AFM image of QDs on Au substrate.

    Fig. S2. Lorentzian line fit of PL spectra.

    Fig. S3. FEM simulation of scattering spectra.

    Fig. S4. 3D FDTD simulation of the optical field enhancement.

    References (5860)

  • Supplementary Materials

    This PDF file includes:

    • Section S1. Characterization of single isolated QDs
    • Section S2. Lorentzian fitting of emission spectra of uncoupled QD and cavity
    • Section S3. A coupled oscillator model for plexciton spectra
    • Section S4. Parameters of model fit
    • Section S5. FEM simulation of strong coupling
    • Section S6. FDTD simulation of optical field distribution in a plasmonic cavity
    • Fig. S1. AFM image of QDs on Au substrate.
    • Fig. S2. Lorentzian line fit of PL spectra.
    • Fig. S3. FEM simulation of scattering spectra.
    • Fig. S4. 3D FDTD simulation of the optical field enhancement.
    • References (5860)

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