Design of a 140 GHz TE_28,8 gyrotron quasi-optical mode converter

This paper designed a hybrid quasi-optical launcher suitable for the 140 GHz TE₂₈,₈ mode based on scalar diffraction integrals and fast Fourier transform theory. It employs the nine coupled modes of the Denisov-type launcher as objective functions and utilizes an adaptive optimization iterative algorithm to maximize the correlation coefficient between the internal wall field distribution and the objective functions, thereby generating arbitrarily shaped internal wall perturbation structures. As a result, the scalar Gaussian content at the radiation aperture reaches 99.2%, and the vector Gaussian content reaches 98.4%. Based on this design, a three-stage mirror system is developed using phase difference algorithms in conjunction with Gaussian beam propagation theory. This system achieves horizontal directional beam radiation with local phase correction. The output beam at the output window exhibits a scalar Gaussian content of 99.7% and a vector Gaussian content of 98.1%. Finally, an analysis was conducted on the installation error of the mirror.