Design of Quasi-Optical Mode Converter for 28GHz Gyrotron

This paper presents the design of two quasi-optical mode converter for gyrotrons to transform the cavity waveguide mode TE 02 and TE 83 into a fundamental Gaussian beam. Those two quasi-optical mode converters are optimized by a combination of three methods, which are the scalar diffraction theorem, the K-S phase-correcting optimization iterative algorithm, and Geometrical Optics. According to the results, the conversion efficiency of energy is 92.5%(TE 02 ) and 95%(TE 83 ) and the Gaussian content of the output beam on the window surface is 99%.