Study on the Terahertz Denisov Quasi-Optical Mode Convertor

Considering the backward waves, the coupled-mode theory for the dimpled-wall Denisov launcher has been developed. The 140-GHz TE28,8 mode was recalculated with this method and the results are consistent with those reported by Thumm's team. With the coupled-mode theory, the Denisov-type quasi-optical mode convertor for 220-GHz TE14,4 mode gyrotron has been investigated, of which the maximal relative power of the backward waves at the launcher cut is just about 0.7%, the power-conversion efficiency is about 95%, and the scalar Gaussian mode contents are 98% at the output window.

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