Ultrafast spontaneous emission source using plasmonic nanoantennas.

Thang B Hoang,David R Smith,Jiani Huang,Maiken H Mikkelsen,Gleb M Akselrod,Christos Argyropoulos

doi:10.1038/ncomms8788

Abstract

Typical emitters such as molecules, quantum dots and semiconductor quantum wells have slow spontaneous emission with lifetimes of 1–10 ns, creating a mismatch with high-speed nanoscale optoelectronic devices such as light-emitting diodes, single-photon sources and lasers. Here we experimentally demonstrate an ultrafast (<11 ps) yet efficient source of spontaneous emission, corresponding to an emission rate exceeding 90 GHz, using a hybrid structure of single plasmonic nanopatch antennas coupled to colloidal quantum dots. The antennas consist of silver nanocubes coupled to a gold film separated by a thin polymer spacer layer and colloidal core–shell quantum dots, a stable and technologically relevant emitter. We show an increase in the spontaneous emission rate of a factor of 880 and simultaneously a 2,300-fold enhancement in the total fluorescence intensity, which indicates a high radiative quantum efficiency of ∼50%. The nanopatch antenna geometry can be tuned from the visible to the near infrared, providing a promising approach for nanophotonics based on ultrafast spontaneous emission.

Highlights

Typical emitters such as molecules, quantum dots and semiconductor quantum wells have slow spontaneous emission with lifetimes of 1–10 ns, creating a mismatch with high-speed nanoscale optoelectronic devices such as light-emitting diodes, single-photon sources and lasers
The nanopatch antennas (NPAs) system consists of a silver nanocube coupled to a metal film, separated by a controlled nanoscale (B10 nm) dielectric spacer layer and colloidal quantum dots (QDs) (Fig. 1a–c)
The fundamental plasmonic mode is a Fabry–Perot resonance resulting from multiple reflections of the waveguide mode beneath the nanocube that propagates within the gap region

Summary

Introduction

Typical emitters such as molecules, quantum dots and semiconductor quantum wells have slow spontaneous emission with lifetimes of 1–10 ns, creating a mismatch with high-speed nanoscale optoelectronic devices such as light-emitting diodes, single-photon sources and lasers. We experimentally demonstrate an ultrafast (o11 ps) yet efficient source of spontaneous emission, corresponding to an emission rate exceeding 90 GHz, using a hybrid structure of single plasmonic nanopatch antennas coupled to colloidal quantum dots. We show an increase in the spontaneous emission rate of a factor of 880 and simultaneously a 2,300-fold enhancement in the total fluorescence intensity, which indicates a high radiative quantum efficiency of B50%. Colloidal QDs have been demonstrated as stable, room temperature singlephoton sources[2,3], but the slow radiative rate associated with these systems limits the attainable repetition rate.

Methods

Results

Conclusion