Spatial mode properties of plasmon assisted transmission
  Orbital angular momentum of photons is explored to study the spatial mode properties of plasmon assisted transmission process. We found that photons carrying different orbital angular momentums have different transmission efficiencies, while the coherence between these spatial modes can be preserved. 
Xi-Feng Ren, Guo-Ping Guo, Yun-Feng Huang, Zhi-Wei Wang, Guang-Can Guo