The influence of finite end screens on the spectrum of oscillations in cylindrical quasioptical dielectric resonators

We have studied the influence of finite dimensions of the end screens on the spectrum of whispering gallery modes in a teflon cylindrical quasioptical resonator. The dependence of the resonance oscillation frequency on the radius of conducting end screens is determined for the first time. Variation of the screen radius leads to transformation of the axial index of HE modes.