Resonant spherical hole in a high loss liquid at millimeter wavelengths

The resonant properties of a quasi-optical spherical hole in a high loss liquid were studied theoretically and experimentally at millimeter wavelengths. The rigorous solutions of Maxwell equations for TE and TM oscillations were obtained as characteristic equations. The numerical solutions of these equations for eigencomplex frequencies and electromagnetic field distribution were found. We were the first who found out that a dielectric spherical hole in a high loss liquid possesses features of a metal cavity resonator. We carried out the experiment to excite TE and TM oscillations in the spherical hole as a resonator into the water. The experimental results agree well with our numerical data for the resonator´s eigenfrequencies. Noneigen surface oscillations similar to the oscillations in the surface Zenneck´s wave are excited in such a resonator. The resonant properties of the dielectric quasi-optical spherical hole in a high loss liquid could be used for measuring the permittivity of liquid.