Channel spaser
  We show that net amplification of surface plasmons is achieved in channel in a metal plate due to nonradiative excitation by quantum dots. This makes possible lossless plasmon transmission lines in the channel as well as the amplification and generation of coherent surface plasmons. As an example, a ring channel spaser is considered. 
A.A. Lisyansky, I.A. Nechepurenko, A.V. Dorofeenko, A.P. Vinogradov,   and A.A. Pukhov
cond-mat.mes-hall