Fig. 1. Schematic diagram of RDSG model structure and dimensions

Fig. 2. Distribution of electric field E_z at the typical frequency of 1.03 THz of RDSG-SWS and DSG-SWS

Fig. 3. Brillouin curves and normalized phase velocity of RDSG-SWS and DSG-SWS

Fig. 4. Interaction impedance of RDSG-SWS and DSG-SWS

Fig. 5. Time-transient solver calculation model in CST MWS

Fig. 6. Transmission properties of RDSG

Fig. 7. PIC simulation results of 26 kV beam voltage

Fig. 8. Frequency versus beam voltage and output power versus frequency of RDSG-SWS and DSG-SWS BWO