Ultrafast and highly collimated radially polarized photons from a colloidal quantum dot in a hybrid nanoantenna at room-temperature

TL;DR

This paper presents a room-temperature, on-chip device that generates highly directional, radially polarized single photons at high rates using a colloidal quantum dot integrated with a hybrid nanoantenna, advancing quantum communication technologies.

Contribution

The study demonstrates a novel hybrid nanoantenna design that achieves ultrafast, highly collimated radially polarized photon emission from colloidal quantum dots at room temperature, with precise positioning critical for polarization purity.

Findings

Achieved >93% radial polarization purity in emitted photons

Demonstrated high emission rates suitable for quantum communication

Validated the importance of quantum dot positioning through experiments and simulations

Abstract

To harness the potential of radially polarized single photons in applications such as high-dimensional quantum key distribution (HD-QKD) and quantum communication, we demonstrate an on-chip, room-temperature device, which generates highly directional radially polarized photons at very high rates. The photons are emitted from a giant CdSe/CdS colloidal quantum dot (gQD) accurately positioned at the tip of a metal nanocone centered inside a hybrid metal-dielectric bullseye antenna. We show that due to the large and selective Purcell enhancement specifically for the out-of-plane optical dipole of the gQD, the emitted photons can have a very high degree of radial polarization (>93%), based on a quantitative metric. Our study emphasizes the importance of accurate gQD positioning for optimal radial polarization purity through extensive experiments and simulations, which contribute to the fundamental understanding of radial polarization in nanostructured devices and pave the way for implementation of such systems in practical applications using structured quantum light.