ABSTRACT
This chapter summarizes various methods invented to compensate or reduce losses in plasmonic materials, including introduction of optical gain and plasmons in direct current electric field. The presence of losses associated with metals places a limitation on the distance over which surface plasmon (SP) –polariton modes may propagate, and these losses are associated with an imaginary part of permittivity. To begin the SPs amplification by stimulated emission of radiation, the radiation from the light pumped excites an electron–hole pair in the gain medium. The theoretical configuration is analyzed to describe the amplification of surface plasmon polariton modes in planar structures using optically pumped gain media. A similar mechanism exists in semiconductors, and dc currents flowing there can transfer kinetic energy of electrons into the energy of terahertz (THz) plasmons, thus creating a solid-state THz source. Essentially, active and passive plasmonic devices are similar to and provide the same role as photonic devices, such as emitters and detectors.
