Coherent control of optical spin-to-orbital angular momentum conversion   in metasurface
  We propose and experimentally demonstrate that a metasurface consisting of Pancharatnam-Berry phase optical elements can enable the full control of optical spin-to-orbital angular momentum conversion. Our approach relies on the critical interference between the transmission and reflection upon the metasurfaceto create actively tunable and controllable conversion with a high output via coherent control of the two incident beams. The introduced control methodology is general and could be an important step toward the development of functional optical devices for practical applications. 
Huifang Zhang, Ming Kang, Xueqian Zhang, Wengao Guo, Changgui Lu,   Yanfeng Li, Weili Zhang, and Jiaguang Han
physics.optics cond-mat.mes-hall