In this paper, the vector field formulas of TEMpi-modes in a concave spherical quasi-opitcal cavity are deduced by the complex-source-point theory. The resonant frequencies of TEMpi-modes are also obtained.
Jun Xiang Ge, Jun Xiang Ge,
"High-order modes in a quasi-optical cavity", Proc. SPIE 1576, 16th International Conference on Infrared and Millimeter Waves, 15765B (1 October 1991); doi: 10.1117/12.2297904; https://doi.org/10.1117/12.2297904