Terahertz surface wave oscillator with tapered slow-wave structure

A terahertz overmoded surface wave oscillator (SWO) with tapered slow wave structures (SWS) added after the uniform SWSs is investigated, and the notable enhancement of output power and mode purity is obtained. At first, the resonant characteristics of the multiple high frequency structure are studied and analyzed by using the S-parameters method. Then a 2.5 dimensional particle-in-cell (PIC) code UNIPIC is employed to simulate and research the variation relations between the output performance of the oscillator and the length of tapered SWSs. The results show that the power ratio of TM01 mode in the output terahertz wave increases to be over 80% with the increase of period number, while ratios of TM02 and TM03 higher modes are suppressed efficiently; and the output power of the oscillator with appropriate length of tapered SWSs is 50% more than that from SWO with uniform SWSs.