Abstract
<title>Abstract</title> <p>Graphene-based spasers have attracted significant interest due to the exceptional properties of monolayer graphene, including its ability to support strongly confined surface plasmons across a broad spectral range and its tunable conductivity via electrical or chemical means. In this work, we propose a novel concept of a random graphene-based spaser, consisting of a graphene monolayer deposited on a silicon–silica random grating substrate. A quantum cascade quantum well acts as the gain medium, where it is placed above the graphene layer. The inherent disorder of the substrate induces Anderson localization of the surface plasmon-polaritons (SPPs) along the graphene, enabling a fundamentally new type of nanoscale random laser which operates via the localized SPPs. Unlike conventional random lasers that rely on multiple photon scattering, the proposed random spaser operates via stimulated amplification of the localized graphene surface plasmons (GSPs), resulting in a coherent emission confined in the nano-scale range. When this structure is pumped optically above the threshold, the gain medium, non-radiatively, transfers its energy to the localized graphene surface plasmons (GSPs), producing an amplified coherent surface emission. This device functions as an efficient, compact mid-infrared nanoscale light source, with highly localized surface-bound modes. This platform paves the way for new applications in nanoscale spectroscopy, nonlinear optics, optoelectronics, and integrated photonic information processing.</p>