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

Korenobu Matsuzaki,Matthew R Buck,Björn Hoffmann,Stephan Götzinger,Anke Dutschke,Silke Christiansen,Hsuan-Wei Liu,Vahid Sandoghdar,Jennifer A Hollingsworth,Simon Vassant,Xuewen Chen

doi:10.1038/srep42307

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.

Highlights

IntroductionOne needs a precise knowledge of the excitation and emission rates, e.g., through careful saturation studies
Fluorescence lifetime measurements are routine, distinction of the radiative and nonradiative decay rates requires further information about the quantum efficiency defined as η = γr/(γr + γnr) both in the absence and presence of the antenna
Theoretical calculations indicate that radiative enhancement factors as large as several thousands are within reach with nanocone antennas if one tunes the wavelength of interest to the near infrared to minimize the losses in gold[35,36]

Summary

Introduction

One needs a precise knowledge of the excitation and emission rates, e.g., through careful saturation studies. Such measurements demand a very high degree of photostability. Multiexcitonic emission paves the way for the realization of brighter sources of photons and exotic states of light with well-defined photon numbers. Processes such as fast Auger recombination usually quench the emission of higher-order excitons and lead to photoblinking[27]. We decipher monoexcitonic and biexcitonic emission processes of a single qdot and show a high performance for both, corresponding to an improvement in the quantum efficiency of the biexciton by more than one order of magnitude

Methods

Results

Conclusion