Power flow in the interior and exterior of cylindrical coated nanoparticles

Electrically small configurations consisting of resonant active coated nanoparticles of a circularly cylindrical shape are considered in the case of a magnetic line source excitation at optical frequencies. The active particles are comprised of a canonical gain-impregnated silica nanocore covered concentrically with a silver, gold, or copper nanoshell.

Particular attention is devoted to both the direction and the magnitude of the power flow density inside and outside of such particles. The results for the active coated nanoparticles are related to those of the corresponding passive designs at optical frequencies, and are further contrasted to the results for the electrically small structures based on epsilon-negative materials at radio frequencies.