Abstract: An orbital angular momentum (OAM) controller controls OAM of a plurality of neutrons and includes: a substrate; a first surface of the substrate; and a second surface of the substrate disposed opposingly across the substrate from the first surface and including a contoured shape. A process for controlling OAM of neutrons includes: subjecting an OAM controller to a plurality of neutrons; receiving the neutrons at a first surface of the OAM controller; transmitting the neutrons through the OAM controller; and providing a phase shift ? to a wavefunction of neutrons transmitted through the OAM controller according to ??T1+T2(?/2?), wherein T1 is a first thickness of a substrate of the OAM controller, T2 is a second thickness of the substrate, and ? is an azimuthal angle of the substrate.