Study of the mode converter for terahertz band vacuum tube

In this paper, a mode converter from rectangular waveguide TE 10 to TEM 00 Mode at Terahertz band is proposed. Firstly, a square-circle transition is used to convert the TE 10 mode in the rectangular waveguide into the TE 11 mode in the circular waveguide. Secondly, based on the coupled wave theory, the TE 11 mode is converted into HE 11 mode through smooth wall circular waveguide. Finally, in terms of the Stratton-Chu formula and mirror optimization program, the structure of the two quasi-optical mirrors which transmit the wave beam to the window successfully has been obtained. The simulation results show that the power transmission efficiency of the designed TE 10 -TEM 00 mode converter from the input of the rectangular waveguide to the vacuum window is 96.1% at a center frequency of 1030 GHz. The designed mode converter has a simple structure and easy to machine.