Spaser with a Three-Level Active Medium Based on a Layered Cylinder

We report a theoretical study of a spaser with an active medium containing three-level molecules or quantum dots, generating one-dimensional axisymmetric plasmon polaritons in a circular cross-section nanowire with a dielectric core and a silver shell. Within the quantum approach to the description of a three-level system and a plasmon polariton, equations of the spaser dynamics are derived and some of their parameters are calculated. The ranges of relaxation rates between excited states of a three-level system are found, at which plasmons of a higher or lower frequency, as well as of both frequencies simultaneously, are generated. It is shown that the stationary number of plasmons of a higher frequency increases linearly with increasing pump rate, and the number of plasmons of a lower frequency either increases nonlinearly or remains constant. Different dependences of the number of plasmons with a higher and lower frequency on the inner radius of the nanowire shell are obtained.