Electromagnetic resonator comprised of annular resonant bodies disposed between confinement plates

An article comprising a resonator for electromagnetic energy comprising

• a) two or more essentially identical annular bodies, a given one of the annular bodies having a thickness t and radial dimension R relative to an axis of the body, said body comprising conductive material and having an outer surface and an inner surface, with a slit extending between said outer and inner surfaces, each of said outer and inner surfaces being substantially parallel with the axis of the given body, said thickness t is aligned along the axial direction and is less than the radial dimension R, said two or more annular bodies being coaxially disposed;
• b) substantially planar end confinement plates for electromagnetic energy, said two or more annular bodies disposed between and spaced from said, end confinement plates;
• c) at least one substantially planar intermediate confinement plate disposed between, and spaced from, two of said two or more annular bodies, said intermediate confinement plate having an opening that facilitates coupling electromagnetic energy between said two adjacent ones of the two or more of the annular bodies, wherein each of said end confinement plates and intermediate confinement plate is disposed such that the axis of the given one of the annular bodies is substantially perpendicular to any of the confinement plates;
• and
• d) means for coupling electromagnetic energy to the resonator, and means for coupling electromagnetic energy from the resonator.