  The introduction of either a central layer defect or a central twist defect
in a periodic structurally chiral material generates
circular-polarization-sensitive spectral holes in the remittance spectrums for
normally incident plane waves. We propose and theoretically establish here the
third method to generate such spectral holes using two-section chiral
sculptured thin films (STFs). Both sections of the proposed device have the
same periodicity and handedness, but their dielectric properties are different
and related in a specific way. The concept of pseudoisotropy is highly relevant
for the production of the proposed device.
