Theory of light scattering in cholesteric blue phases

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Abstract
A comprehensive analysis of elastic light scattering in cholesteric liquid-crystal systems, based upon the Mueller matrix approach, is given. Emphasis is placed upon analyzing the polarization state of the scattered light for arbitrarily polarized incident radiation. The theory is applied to the ordered cholesteric blue phases BPI and BPII, which exhibit long-range orientational ordering. Both the polycrystalline and single-crystal cases are considered and the role played by optical activity is studied. It is shown how light-scattering studies yield information on the structural properties of the ordered phases. The quasielastic light scattering due to excitations in the disordered phase is also analyzed in the harmonic approximation. It is shown that this scattering cannot explain the strong anomolous scattering observed in the amorphous BPIII phase.