Elliptical hole-coupling optical resonator in THz FEL

The scheme of elliptical hole-coupling optical resonator is proposed instead of circular hole-coupling resonator which is used in THz FEL in order to increase the output power and resonator quality. Three-dimensional simulations and design on elliptical hole-coupling optical resonator are carried out using our 3D OSIFEL code. It is proved that the elliptical hole-coupling optical resonator is effective and applicable for the THz FEL. Using elliptical hole-coupling optical resonator, the output power can be increased by more than 33%, and the coupling efficiency of resonator can be increased almost by 30%-70%. The superiority of elliptical hole-coupling optical resonator will be more prominent with radiation frequency increasing.