Generation of Slow Surface Plasmon Polaritons in a Complex Waveguide Structure with Electric Current Pump

A planar spaser structure composed of semiconducting film and graphene with DC current is proposed and theoretically explored. Graphene possesses velocity of drift current carriers comparable with the phase velocity of surface plasmon polaritons (SPPs) in ultrathin semiconducting film at the terahertz regime. When the synchronism condition between current and slow surface electromagnetic waves is realized, the amplification of plasmons by electric current takes place. In the proposed complex waveguide structure, positive feedback is realized due to reflections from the edges of the active waveguide, and the SPPs are decoupled into light by a microscopic grating manufactured on the semiconducting film surface. The principle of a terahertz spaser is proposed using a semiconductor/graphene waveguide structure. Surface plasmon polariton (SPP) amplification is created by fast drift currents in the graphene, and feedback is provided by the wave reflections at the waveguide ends. Far‐field radiation emission via an adjacent passive waveguide with a diffraction grating is discussed, and the conditions of the SPP generation are analyzed.