Making a curved metallic grating for matching angular divergence of incident radiation includes: providing a mandrel with a curved receiving surface; disposing a planar substrate on the curved receiving surface; applying a clamping force to the planar substrate at the planar field surface; bending the planar substrate to shape-wise conform to the radius of curvature of the curved receiving surface of the mandrel in response to applying the clamping force, such that the planar substrate changes to a curved substrate; and superconformally filling the recessed feature with a metallic superconformal filling comprising a metal to form the curved metallic grating.