Free-Space Optical Beam Tapping with an All-Silica Metasurface

Extraction of information about the multidimensional optical properties of free-space and guided optical beams is critical in modern photonics. To date, planar, most beam-information detection systems destroy or substantially modify the original wave fronts of an incident beam in the detection process. Here, we demonstrate an all-silica beam information detection system that effectively taps into a free space optical beam while leaving the original wavefronts virtually unaffected. This is accomplished by diverting a small (few percent) fraction of the light through the interaction with a silica metasurface based on the Pancharatnam-Berry phase. A chiroptical spectrometer and a multichannel angular momentum detector are proposed to demonstrate the multifunctionality of this design principle. The concept and device proposed here may pave the way to in situ beam monitoring and may provide a novel method to collect optical information for emerging augmented reality technologies.