Sub-THz beam-shaping mirror system designs for Quasi-Optical mode converters in high-power gyrotrons

Methods, algorithms and theories required in sub-THz beam-shaping mirror designs for Quasi-Optical (QO) mode converters (launchers) in high-power gyrotrons are presented in this article. The state-of-the-art design procedure highlights many novel ideas like the Iterative Phase Retrieval (IPR) technique, the Taylor-Interpolation FFT (TI-FFT) algorithm and the iterative Geometrical Optical Phase Correction (GOPC) method, which ensure fast, reliable, flexible and accurate sub-THz beam-shaping mirror system designs in the high-power gyrotron applications. The efficiency of the sub-THz beam-shaping mirror system procedure has been successfully tested in a sub-THz beam-shaping 4-mirror system design for a single-mode (TE22,6/110GHz), 1.25 MW CPI gyrotron to shape the input beam from a QO launcher into the target Fundamental Gaussian Beam (FGB) to be injected into the corrugated waveguide through the diamond window, with up to 99.85% coupling between the designed output beam and the target FGB.