Nonlinearity and optical bistability caused by local field effects in the interaction between a two level atomic system and a metamaterial

TL;DR

This paper theoretically investigates the nonlinear optical response and bistability in a metamaterial coupled with a two-level atomic system, highlighting the effects of local field interactions and nonlinear damping.

Contribution

It provides a detailed analysis of the nonlinear susceptibilities and conditions for optical bistability in a coupled metamaterial-atom system, revealing the unfeasibility of bistability at realistic densities.

Findings

Nonlinear damping reduces spiking effects.

Optical bistability requires unrealistically high atomic densities.

The system's nonlinear response depends on external electric field strength.

Abstract

We present a theoretical analysis of the nonlinear response of a metamaterial consisting of an array of split ring resonators coupled to a two level atomic system (2LS) without inversion. We calculated the total complex susceptibility and the linear, third and fifth-order nonlinear solution of the Maxwell Bloch equations that describe the coupled system. We analyzed the impact of the nonlinear effects on the dynamics of an active metamaterial/2LS compound in dependence of the magnitude of the external electric field when the 2LS is pumped by an external pump source and population inversion is achieved. We observed that nonlinear damping in the active metamaterial/2LS compound significantly reduces the effect of spiking. Finally, we investigated the conditions under which the system can exhibit the phenomenon of optical bistability. We observed that optical bistability can only be obtained when the atomic volume density of the 2LS attains unphysically high values and thus is not expected in the system under investigation.