Characters of frequency response of TM mode with the Tapered Double Sinusoidal Grooves structure operating at 0.35THz frequency

In order to construct a cavity with a high-frequency and high-order single TM operating mode and also are favorable to the mode selectivity, the tapered double sinusoidal grooves structure is proposed. On the basis of ordinary sinusoidal grooves structure, the auxiliary sinusoidal distribution with smaller etching period is superimposed, and the taper is added on the inner and outer conductor walls to form the tapered double sinusoidal grooves coaxial Bragg structure. Through the FORTRAN software programming simulation experiments, we can see that it is different from the working mode TE mode. When the positive taper double sinusoidal grooves is adopted, the band gap overlap phenomenon deteriorates. The use of negative taper double sinusoidal grooves coaxial Bragg structure as the reflector can effectively suppress the band gap overlap phenomenon, the bandwidth gradually becomes wider as the increase of the taper angle, and the working mode TM 62 and the competition mode TE 61 can further separate. This provides a theoretical reference for the design of a coaxial Bragg reflector with a high-frequency and high-order single TM operating mode.