Active individual nanoresonators optimized for lasing and spasing operation

TL;DR

This paper optimizes plasmonic nanoresonators with gold nanorods and core-shell structures for enhanced lasing and spasing, revealing trade-offs in efficiency, thresholds, and bandwidths based on geometry and concentration.

Contribution

It introduces optimized designs of nanoresonators for improved lasing and spasing, analyzing their performance and mode coupling effects.

Findings

Nanorod nanoresonators have lower lasing thresholds and higher near-field intensities.

Core-shell nanoresonators exhibit smaller thresholds and larger quantum efficiencies at higher concentrations.

Strong coupling of plasmonic modes is linked to the transition from lasing to spasing.

Abstract

Plasmonic nanoresonators consisting of a gold nanorod and a spherical silica-core and gold-shell, both coated by a gain layer, were optimized to maximize the near-field enhancement (NF-type) and far-field outcoupling (FF-type), and to enter into the spasing operation region (NF-c*-type). It was shown that in case of moderate concentration the nanorod has more advantages: smaller lasing threshold, larger slope efficiency and achieved intensities in the near-field, in addition in FF-type system smaller gain and outflow threshold, earlier flipping and larger far-field out-coupling efficiency. However, the near-field (far-field) bandwidth is smaller in for NF-type (FF-type) core-shell nanoresonators. In case of larger concentration although the slope efficiency and near-field intensity remain larger and the far-field redistribution is more efficient in case of the nanorod, the core-shell nanoresonator is more advantageous, taking into account the smaller lasing, outflow, absorption and extinction cross-section thresholds, as well as the larger internal and external quantum efficiencies. In addition to this the bandwidth of core-shell nanoresonator is also smaller. It was also shown that the strong-coupling of time-competing plasmonic modes accompanies the transition from lasing to spasing.