Fig. 1. Schematic arrangement of the quasi-optical mode converter

Fig. 2. Field distribution on the wall of the launcher for 105 GHz TE_18,7 and 140 GHz TE_24,9 gyrotron (in dB), the edges of the launcher aperture and cut are indicated

Fig. 3. Profile of the wall surface of the dual-frequency launcher for 105 GHz TE_18,7 and 140 GHz TE_24,9 gyrotron

Fig. 4. E-field distribution on a cylinder with radius of 5 cm in the same coordinate system as the launcher(in dB)

Fig. 5. Design procedure of the phase correction mirror

Fig. 6. Side view of the E-field of the whole system along the center symmetry xz plane obtained from simulation（in dB）

Fig. 7. Contour plots of the E-field on the window plane. The contours are in 3 dB increments