@article {25302,
	title = {Terahertz frequency- and mode-insensitive broadband quasi-optical converter antenna system},
	journal = {ournal of Infrared Millimeter and Terahertz Waves},
	volume = {39},
	year = {2018},
	pages = {1065-1078},
	abstract = {Recently emerged multimode gyrotron, a high-power broadband terahertz radiator, encounters the challenge of efficiently converting a series of operating whispering-gallery modes (WGMs) into free-space Gaussian beams. To this demand, we propose a frequency- and mode-insensitive antenna capable of broadband multimode converting. For a single mode, to achieve broadband operation, special reflector configuration and large-radius launcher guarantee the system high robustness to frequency-induced wave number variation. Furthermore, for a series of operating WGMs, in order to achieve multimode operation, high-order mode indices guarantees familiar field patterns and ray trajectories. In particular, high-purity Gaussian beams are simultaneously achieved in different WGMs of broad continuous bands, including 351{\textendash}361\&nbsp;GHz for TE11,2\&nbsp;mode, 375{\textendash}385\&nbsp;GHz for TE12,2\&nbsp;mode, and 398{\textendash}410\&nbsp;GHz for TE13,2\&nbsp;mode. The results are verified by both the vector diffraction theory and the method of momentum. This kind of mode converter will promote the development of multimode gyrotrons and other antenna-feeder systems for high-power terahertz applications.},
	url = {https://link.springer.com/article/10.1007/s10762-018-0523-1},
	author = {Hui-Qi Bian and Chao-Hai Du* and Shi Pan and Pu-Kun Liu*}
}
