  A Teflon (Polytetrafluoroethylene, PTFE) sphere can be used as a focusing
lens in the applications of imaging and sensing due to its low-loss property in
the terahertz (THz) band. In this paper, we analytically calculated field
intensities and focusing parameters for Teflon spheres at different low-loss
levels and then discovered a super-enhancement focusing effect in the spheres
with particular size parameters, which can stimulate about 4000 times stronger
field intensity than that for incident radiation as well as the great potential
of overcoming diffraction limit despite high sensitivity to the magnitude of
Teflon loss. A subsequent analysis of scattering amplitudes proved that the
strong scattering of a single order mode in the internal electric or magnetic
field is the main factor causing this phenomenon.
