Plasmon-assisted transmission of high-dimensional orbital angular-momentum entangled state

We present an experimental evidence that high-dimensional orbital angular-momentum entanglement of a pair of photons can be survived after a photon-plasmon-photon conversion. The information of spatial modes can be coherently transmitted by surface plasmons. This experiment primarily studies the high-dimensional entangled systems based on surface plasmon with subwavelength structures. It maybe useful in the investigation of spatial-mode properties of surface plasmon-assisted transmission through subwavelength hole arrays.