Unique optical properties of anisotropic helical structures in a Fabry-Perot cavity

Anisotropic helical structures in Fabry-Perot (FP) cavities are shown to exhibit unique properties. The FP peaks are unpolarized, consisting of doublets corresponding to Bloch-Lyaponov eigenwaves with increased splitting as the local anisotropy increases and as they become closer to the photonic bandgap. The Bragg-type selective reflection peak existing in a free-cavity sample is inhibited when the helical medium is inside a cavity, and it has no effect on the cavity modes. Hence the unique characteristics are obtained even with a single period of the helix, and consequently thin films of helical liquid crystals can be used to build fast tunable polarization insensitive FP filters.