Spaser operation below threshold: autonomous vs. driven spasers

TL;DR

This paper investigates how driven spasers can operate below the threshold by compensating losses with an external optical wave, leading to increased coherent plasmons and reduced quantum noise, unlike autonomous spasers.

Contribution

It demonstrates that external driving can enhance coherence and suppress noise in spasers operating below threshold, a novel approach to spaser control.

Findings

Driven spasers increase coherent plasmons significantly.

Loss compensation reduces quantum noise.

Coherent plasmons can surpass spontaneous plasmons at feasible pump rates.

Abstract

At the plasmon resonance, high Joule losses in a metal nanoparticle of a spaser result in its low Q-factor. Due to the latter, to achieve the spasing regime, in which the number of coherent plasmons exceeds the number of incoherent plasmons, unsustainably high pump rates may be required. We show that under the condition of loss compensation by a spaser driven by an external optical wave, the number of coherent plasmons increases dramatically, and the quantum noise is suppressed. Since the compensation of losses of the driving wave may occur even near the spasing threshold, the number of coherent plasmons may exceed the number of spontaneously excited plasmons at achievable pump rates.