Gain-compensated metal cavity modes and a million-fold improvement of Purcell factors

TL;DR

This paper introduces a rigorous mode theory for gain-compensated plasmonic dimers, achieving over a million-fold increase in Purcell factors and significantly enhancing quality factors, surpassing fundamental limits of lossy media.

Contribution

The work provides a novel theoretical framework and full 3D calculations demonstrating dramatic enhancement of Purcell factors in gain-compensated plasmonic cavities.

Findings

Quality factors increased from 10 to over 26,000

Purcell factors boosted from 3,000 to over 10 billion

Effective mode volume and radiative beta factors remain stable

Abstract

Using a rigorous mode theory for gain-compensated plasmonic dimers, we demonstrate how quality factors and Purcell factors can be dramatically increased, improving the quality factors from 10 to over 26,000 and the peak Purcell factors from around 3000 to over 10 billion. Full three-dimensional calculations are presented for gold dimers in a finite-size gain medium, which allows one to easily surpass fundamental Purcell factor limits of lossy media. Within a regime of linear system response, we show how the Purcell factors are modified from the contributions from the projected local density of states as well as a non-local gain. Further, we show that the effective mode volume and radiative beta factors remain relatively constant, despite the significant enhancement of the Purcell factors.