Devices, systems and methods for creating and demodulating orbital angular momentum in electromagnetic waves and signals

Orbital angular momentum (OAM) communications systems provide an additional degree of freedom to the electromagnetic waves that travel between the transmission and receiving stations, thereby enabling a dramatic increase in data transmission rates. The present invention provides a design for a very low reflectivity flat spiral phase plate that generates OAM modes and a method of making the same. The design incorporates variable sizes of perforated unit cells and may include matched layers to provide improved impedance matching, and the flat disc shape makes the phase plate compact and easy to install. The OAM phase plate can be designed to operate at frequencies from a few 100s KHz to ultraviolet frequencies and is capable of providing one or more OAM modes at the operational frequencies, irrespective of polarization. In a preferred embodiment, the OAM phase plate is designed for operation at about 30 GHz frequency, with 20 GHz bandwidth.