Strong plasmonic enhancement of biexciton emission: controlled coupling of a single quantum dot to a gold nanocone antenna

Abstract

Multiexcitonic transitions and emission of several photons per excitation comprise a very attractive feature of semiconductor quantum dots for optoelectronics applications. However, these higher-order radiative processes are usually quenched in colloidal quantum dots by Auger and other nonradiative decay channels. To increase the multiexcitonic quantum efficiency, several groups have explored plasmonic enhancement, so far with moderate results. By controlled positioning of individual quantum dots in the near field of gold nanocone antennas, we enhance the radiative decay rates of monoexcitons and biexcitons by 109 and 100 folds at quantum efficiencies of 60 and 70%, respectively, in very good agreement with the outcome of numerical calculations. We discuss the implications of our work for future fundamental and applied research in nano-optics.

Numerical analysis of tip-localized surface plasmon resonances in periodic arrays of gold nanowires with triangular cross section

“…The absorption increases up to 95% at the critical angle (marker R0) and also along the solid blue line between labels R0 and R1 that represents the Bragg condition [Eq. (2)]. This enhancement of the absorption in the array of metallic nanowires is similar to observations made with corrugated metallic gratings.…”

“…Such nanotips present an extraordinary enhancement of the electromagnetic field relative to the electromagnetic incident field in the vicinity of their apex. In metallic nanoparticles and nanowires, this enhancement is caused by the excitation of localized surface plasmon resonances (LSPRs) polarized along their tip axis [2]. Furthermore, the spectral line shape, amplitude, and width of the LSPR can be tuned by modifying the aspect ratio [3] and radius of curvature [4] of the nanotips, as well as the refractive index of the surrounding medium [5].…”

Unidirectional, Ultrafast, and Bright Spontaneous Emission Source Enabled By a Hybrid Plasmonic Nanoantenna

“…Thus, the poor emission directionality and long lifetime (corresponding to the slow decay) are two main challenges for practical applications based on spontaneous emission. The use of plasmonic nanoantennas with nanocavities is one of the most effective solutions to obtain ultrafast spontaneous emission due to their ability to extremely localize and enhance the photon density of states, which in turn results in enhanced spontaneous emission due to the Purcell effect . On the other hand, an optical antenna is able to couple the emitted light into the antenna modes and then reradiate photons into specific spatial directions.…”

Cooperative Energy Transfer Controls the Spontaneous Emission Rate Beyond Field Enhancement Limits

“…Figure 4b shows the calculated vs. measured Γ , which are in close agreement, indicating that the slope of SE rate intensity dependence is proportional to the energy transfer rate of individual emitters, as predicted by the proposed CET mechanism. For relatively higher intensities, the rate ratio Γ /Γ exceeds 3 likely because excitons saturate at lower intensities compared to biexcitons [32]. We provide the same analysis presented in Fig.…”