Experimental Test on a Broadband Sub-Terahertz Quasi-Optical Mode Converter for High-Order Confocal Mode

Motivated by transforming the high power output of confocal gyrotron into Gaussian beam, a broadband sub-terahertz quasi-optical mode converter for a high-order confocal waveguide mode is experimental tested and reported in this paper. Driven by a confocal mode generator with limited bandwidth, the measured scalar Gaussian contents are above 90% over a frequency range of 7.2 GHz. The low-power tested result is in good agreement with the simulation result.