Theory of light amplification in active fishnet metamaterials

TL;DR

This paper develops a microscopic theory explaining how active fishnet metamaterials amplify light, highlighting the balance of gain and loss channels that enable steady-state amplification.

Contribution

It introduces an ab initio approach to analyze light amplification in active metamaterials based on Poynting's theorem and microscopic field calculations.

Findings

Radiative loss and gain surpass resistive loss by over two times.

Steady-state amplification is achievable even with metal gain reduction.

The theory links microscopic energy rates to macroscopic amplification behavior.

Abstract

We establish a theory that traces light amplification in an active double-fishnet metamaterial back to its microscopic origins. Based on ab initio calculations of the light/plasmon fields we extract energy rates and conversion efficiencies associated with gain/loss channels directly from Poynting's theorem. We find that for the negative refactive index mode both radiative loss and gain outweigh resistive loss by more than a factor of two, opening a broad window of steady-state amplification (free of instabilities) accessible even when a gain reduction close to the metal is taken into account.