Numerical study of the remittances of axially excited chiral sculptured zirconia thin films

The transmission and reflection spectra from a right-handed chiral sculptured zirconia thin film are calculated using the coupled wave theory and the Bruggeman homogenization formalism in conjunction with the experimental data for the relative dielectric constant of zirconia thin film. The dielectric dispersion function effect on these spectra appeared in wavelengths shorter than the Bragg wavelength. In wavelengths larger than the Bragg wavelength, the dispersion of the dielectric function can be ignored. The results achieved in this work are consistent with the experimental data [Wu, Q.; Hodgkinson, I.J.; Lakhtakia, A. Opt. Eng. 2000, 39, 1863]. A shift towards shorter wavelengths is observed for the Bragg peak with increasing void fraction, which is in agreement with the theoretical work of Lakhtakia [Microw. Opt. Technol. Lett. 2000, 24, 239]. Sorge et al. [Opt. Express 2006, 14, 10550] also found this effect in their experimental results on TiO2 chiral thin films, while they also found that unlike our results the intensity of the reflectance of the Bragg peak decreases with increasing void fraction. This difference between our theoretical work and Sorge et al.'s experimental work can be related to the structural difference between the idealized theoretical model for chiral films and that obtained in experimental work. In the latter, as Sorge et al. have pointed out the experimental films exhibit a large amount of scattering due to the highly complex and non-ideal structure that the individual chiral elements exhibit.