Colloidal-quantum-dot spasers and plasmonic amplifiers

TL;DR

This paper introduces a flexible quantum-dot-based spaser platform that decouples gain from the cavity, enabling controlled plasmon generation and manipulation for diverse on-chip plasmonic applications.

Contribution

It develops a new open architecture for quantum-dot spasers, decoupling gain and cavity, and demonstrates high-quality plasmonic cavities with controlled plasmon generation.

Findings

Successful creation of high-quality Ag plasmonic cavities.

Effective incorporation of quantum dots for plasmon generation.

Demonstration of controlled plasmon amplification and focusing.

Abstract

Colloidal quantum dots are robust, efficient, and tunable emitters now used in lighting, displays, and lasers. Consequently, when the spaser, a laser-like source of surface plasmons, was first proposed, quantum dots were specified as the ideal plasmonic gain medium. Subsequent spaser designs, however, have required a single material to simultaneously provide gain and define the plasmonic cavity, an approach ill-suited to quantum dots and other colloidal nanomaterials. Here we develop a more open architecture that decouples the gain medium from the cavity, leading to a versatile class of quantum-dot-based spasers that allow controlled generation, extraction, and manipulation of plasmons. We first create high-quality-factor, aberration-corrected, Ag plasmonic cavities. We then incorporate quantum dots via electrohydrodynamic printing18,19 or drop-casting. Photoexcitation under ambient conditions generates monochromatic plasmons above threshold. This signal is extracted, directed through an integrated amplifier, and focused at a nearby nanoscale tip, generating intense electromagnetic fields. This spaser platform, deployable at different wavelengths, size scales, and geometries, can enable more complex on-chip plasmonic devices.