Three-dimensional measurements of a millimeter wave orbital angular momentum vortex

Initial three-dimensional phase and intensity measurements of a 100 GHz l=±1 orbital angular momentum (OAM) vortex are presented. The vortex was generated by illuminating a polypropylene spiral phase plate. Measurements were taken with a three-dimensional field scanner operating in the W-band (75–100 GHz). Early analysis shows splitting of the OAM phase dislocation at the vortex center, resulting in a complex inner vortex intensity pattern.