Efficient wide-angle broadband blazed gratings enabled by metasurfaces

Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering. Here, we experimentally demonstrate a metasurface-based wide-angle broadband all-dielectric blazed grating with an extreme incident angle of up to 80°, which is achieved by optimizing the wide-angle phase shifts and transmissivities of the unit cells. It exhibits a maximum diffraction efficiency of 72% and a high average efficiency of 64% over a wide range of incident angles from −80° to 45° at 1.55 μm. Moreover, the proposed grating has a broad bandwidth of 200 nm (1.45–1.65 μm), and average efficiencies of more than 50% can be achieved experimentally over the same incidence angles. Our results may pave the way for the creation of novel and efficient flat optical devices for wavefront control.