Spaser and Optical Amplification Conditions in Graphene-Coated Active Wires

This work analyzes the optical properties of a localized surface plasmon (LSP) spaser made of a dielectric active wire coated with a graphene monolayer. Our theoretical results, obtained by using rigorous electromagnetic methods, illustrate the non-radiative transfer between the active medium and the localized surface plasmons of the graphene. In particular, we focus on the lasing conditions and the tunability of the LSP spaser in two cases: when the wire is made of an infrared/THz transparent dielectric material and when it is made of a metal-like material. We analyze the results by comparing them with analytical expressions obtained by us using the quasistatic approximation. We show that the studied systems present a high tunability of the spaser resonances with the geometrical parameters as well as with the chemical potential of the graphene.