A customizable class of colloidal-quantum-dot metallic lasers and amplifiers

• Published in: Science advances Vol. 3; no. 9
• Main Authors: Kress, Stephan J. P., Cui, Jian, Rohner, Patrik, Kim, David K., Antolinez, Felipe V., Zaininger, Karl-Augustin, Jayanti, Sriharsha V., Richner, Patrizia, McPeak, Kevin M., Poulikakos, Dimos, Norris, David J.
• Format: Journal Article
• Language: English
• Published: 01.09.2017
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.1700688

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 high-intensity, narrow-band surface plasmons—was first proposed, quantum dots were specified as the ideal plasmonic gain medium for overcoming the significant intrinsic losses of plasmons. Many subsequent spasers, however, have required a single material to simultaneously provide gain and define the plasmonic cavity, a design unable to accommodate quantum dots and other colloidal nanomaterials. In addition, these and other designs have been ill suited for integration with other elements in a larger plasmonic circuit, limiting their use. We develop a more open architecture that decouples the gain medium from the cavity, leading to a versatile class of quantum dot–based metallic lasers that allow controlled generation, extraction, and manipulation of electromagnetic waves. We first create aberration-corrected plasmonic cavities with high quality factors at desired locations on an ultrasmooth silver substrate. We then incorporate quantum dots into these cavities via electrohydrodynamic printing or drop-casting. Photoexcitation under ambient conditions generates monochromatic light (0.65-nm linewidth at 630 nm, Q ~ 1000) above threshold. This signal is extracted, directed through an integrated amplifier, and focused at a nearby nanoscale tip, generating intense electromagnetic fields. More generally, our device platform can be straightforwardly deployed at different wavelengths, size scales, and geometries on large-area chips for fundamental studies and applications. Colloidal quantum dots in silver cavities result in a versatile class of laser-like plasmonic devices for on-chip use.