Spaser Action, Loss Compensation, and Stability in Plasmonic Systems with Gain

TL;DR

This paper shows that in plasmonic systems with gain, full loss compensation inevitably leads to instability and spaser generation, establishing a universal criterion for loss overcompensation.

Contribution

It provides an analytical, geometry-independent criterion linking loss compensation and spaser instability in plasmonic-gain systems.

Findings

Full loss compensation causes instability and spasing.

The loss overcompensation criterion is universal and analytical.

Limits on maximum loss compensation are identified.

Abstract

We demonstrate that the conditions of spaser generation and the full loss compensation in a resonant plasmonic-gain medium (metamaterial) are identical. Consequently, attempting the full compensation or overcompensation of losses by gain will lead to instability and a transition to a spaser state. This will limit (clamp) the inversion and lead to the limitation on the maximum loss compensation achievable. The criterion of the loss overcompensation, leading to the instability and spasing, is given in a analytical and universal (independent from system's geometry) form.