Coupling of guided Surface Plasmon Polaritons to proximal self-assembled InGaAs Quantum Dots

TL;DR

This study investigates how guided surface plasmon polaritons along gold waveguides on GaAs substrates can be coupled to near-surface InGaAs quantum dots, demonstrating potential for nanoscale quantum optics applications.

Contribution

It introduces a method to couple surface plasmon polaritons with self-assembled quantum dots and measures their propagation lengths and energy transfer characteristics.

Findings

Surface plasmon propagation lengths range from 13.4 to 27.5 micrometers.

Plasmons can excite quantum dots, enabling spatial imaging of plasmon modes.

Unidirectional energy transfer from plasmons to quantum dots was observed.

Abstract

We present investigations of the propagation length of guided surface plasmon polaritons along Au waveguides on GaAs and their coupling to near surface InGaAs self-assembled quantum dots. Our results reveal surface plasmon propagation lengths ranging from 13.4 {\pm} 1.7 {\mu}m to 27.5 {\pm} 1.5 {\mu}m as the width of the waveguide increases from 2-5 {\mu}m. Experiments performed on active structures containing near surface quantum dots clearly show that the propagating plasmon mode excites the dot, providing a new method to spatially image the surface plasmon mode. We use low temperature confocal microscopy with polarization control in the excitation and detection channel. After excitation, plasmons propagate along the waveguide and are scattered into the far field at the end. By comparing length and width evolution of the waveguide losses we determine the plasmon propagation length to be 27.5 {\pm} 1.5 {\mu}m at 830 nm (for a width of 5 {\mu}m), reducing to 13.4 {\pm} 1.7 {\mu}m for a width of 2 {\mu}m. For active structures containing low density InGaAs quantum dots at a precisely controlled distance 7-120 nm from the Au-GaAs interface, we probed the mutual coupling between the quantum dot and plasmon mode. These investigations reveal a unidirectional energy transfer from the propagating surface plasmon to the quantum dot. The exquisite control of the position and shape afforded by lithography combined with near surface QDs promises efficient on-chip generation and guiding of single plasmons for future applications in nanoscale quantum optics operating below the diffraction limit.