Holographic detection of the orbital angularmomentum of light with plasmonic photodiodes

摘要

Metallic components such as plasmonic gratings and plasmonic lenses are routinely used toconvert free-space beams into propagating surface plasmon polaritons and vice versa. Thisgeneration of couplers handles relatively simple light beams, such as plane waves or Gaussianbeams. Here we present a powerful generalization of this strategy to more complex wavefronts, such as vortex beams that carry orbital angular momentum, also known as topologicalcharge. This approach is based on the principle of holography: the coupler is designed as theinterference pattern of the incident vortex beam and focused surface plasmon polaritons. Wehave integrated these holographic plasmonic interfaces into commercial silicon photodiodes,and demonstrated that such devices can selectively detect the orbital angular momentum oflight. This holographic approach is very general and can be used to selectively couple freespace beams into any type of surface wave, such as focused surface plasmon polaritons andplasmonic Airy beams.