Specular and nonspecular, thickness-dependent, spectral holes in a slanted chiral sculptured thin film with a central twist defect

We demonstrate analytically that two types of spectral holes located approximately in the center of the Bragg regime could be exhibited by a slanted chiral sculptured thin film (STF) containing a 90degrees twist defect midway through its thickness. One is a nonspecular spectral reflection hole excited by an incident circularly polarized plane wave of the same handedness as the chiral slanted STF, and the other a specular transmission hole excited by an incident circularly polarized plane wave of the opposite handedness. The occurrences of these holes depend on the device thickness, and a crossover thickness can be defined. The existence of both types of spectral holes is sensitive to the dual-periodicity of the slanted chiral STF, and can be completely subverted by the Rayleigh-Wood phenomenon. (C) 2002 Elsevier Science B.V. All rights reserved.