Third method for generation of spectral holes in chiral sculptured thin films

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.