Chiral photonic film and flake

We show that chiral photonic flake has potential as a physical effect colorant that contributes both bright interference colors and a characteristic polarization spectrum. An analysis of the polarizing properties of chiral film and flake indicates that the Stokes spectrum s(3) v. lambda is suitable for characterization. s(3) is shown to be invariant both to azimuthal rotation of a flake and to incoherent summation of the light from an array of flakes with random orientations. We form chiral photonic flake experimentally by scraping film material from nanoengineered chiral films on glass. Three basic architectures are used, a standard chiral medium that supports a single Bragg resonance, a threaded chiral medium that supports right-handed and left-handed resonances at different wavelengths and a threaded chiral medium that supports two right-handed resonances at different wavelengths. In a separate set of experiments a twist defect is added to each basic structure. Experimental measurements of s(3) spectra from film and flake show the expected signatures of the circular Bragg resonances and of the spectral holes caused by the defects. (C) 2008 Optical Society of America