Tunable spherical graphene surface plasmon amplification by stimulated emission of radiation

A structure is suggested for spasing. The presented surface plasmon amplification by stimulated emission of Radiation (SPASER) is made up of a graphene nanosphere, which supports localized surface plasmon modes, and a quantum dot array, acting as a gain medium. The gain medium is pumped by an external light source. Since all the plasmons are carried on a graphene platform, the structure features coherent surface plasmons with high confinement and large life time. All the structures are analyzed theoretically using full quantum mechanical description. The main advantage of the proposed SPASER is its simple tuning capability of changing graphene's Fermi level, which is performed by either chemical doping in the manufacturing time or electrostatic gating. We suggest the utilization of the proposed SPASER for exciting coherent long-range surface plasmons on a graphene sheet. The near field of the SPASER couples to the surface plasmons on graphene sheet and compensates the large momentum mismatch between surface plasmons and photons. (C) 2019 Society of PhotoOptical Instrumentation Engineers (SPIE).