Phase retrieval of high-power gyrotron orbital angular momentum beams

We present an effective phase retrieval technique for determining the vortex charge of a high-power orbital angular momentum (OAM) beam based on phase coefficients optimization. The high-power OAM beam is generated by transmitting a 25 kW, 95 GHz Gaussian like gyrotron beam through a spiral phase plate (SPP). Determination of the vortex charge of the OAM beam is carried out using a modified phase retrieval algorithm. Retrieved intensity profile show 99.27% intensity regeneration at measurement planes for the high-power OAM beam.