Abstract
The thesis containing design and fabricate the TE01 mode convert at THz band to establish a high-efficiency and high-precision X-ray lightgrophy technique. The technique is application to fabricate TE01 mode convert of 0.238mm thickness at THz band, and this mode convert can be used to provide a purity TE01 source for a low-loss cylinder waveguide. At design part, we use high-frequency structure simulation(Ansoft HFSS 13.0) to design our element. Due to TE01 mode is high order mode in cylindrical waveguide, so we using side wall coupling way (Y-type structure) to excite it. As the injected THz wave (TE10) travels to the first power-dividing junction, it would be split into two signals with equal amplitudes and phases. These two signals keep propagating forward and will be subsequently divided into four sub-signals by the additional two power dividers (Y-shaped). The four arms of the second-stage power dividers finally attach on the side wall of cylindrical waveguide with the symmetric spatial orientations. When the foul equal-amplitude and equal-phase TE10 waves are led into this mode-converting section, their linearly-polarized electric fields circumnavigate the cylindrical waveguide and hence jointly excite the TE01. Finally, the very high-purity circular TE01 mode will emerges at the output end. At fabricate part, we use LIGA process to fabricate the mode convert, and we select KMPR as our photoresist because it can be removed easier than SU-8 by chemical method.