q-plate for millimeter-wave orbital angular momentum manipulation.

q-plates are quasi-optical devices specifically designed to generate and detect the orbital angular momentum states of the light. It is possible to produce q-plates working at millimeter wavelengths by using a well-known and cheap manufacturing technique. The technique consists of creating inhomogeneous, artificial birefringent materials by machining grooves with specific geometries into normal dielectric materials. In this work, a q-plate working around 100 GHz has been designed, manufactured, and tested using a vector network analyzer. The experimental data validate the modeled intensity and phase for the transformation of an incident Gaussian beam.