Position sensitive lasing with continuous wavelength tunability and emission in the cell-plane direction is demonstrated from a photopolymerized cholesteric liquid crystal film. The device has a gradually dilating helix lying in the cell-plane direction and is fabricated by applying a vertical electric field in a conventionally rubbed wedge cell while cooling the sample from the isotropic phase. Tuning range of ∼100nm is achieved by translating the device with respect to the pump beam. Photopolymerizable materials are especially useful in this configuration since a freestanding film, not requiring any external voltage to maintain the molecular ordering, can be prepared.

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We report an anomalous destruction of cholesteric blue phases I and II upon photopolymerizing a liquid crystal mixture composed of mono- and diacrylate monomers. The platelet texture characteristic of the blue phase collapsed when the sample was irradiated by a weak UV light source, while usual freezing of both blue phases I and II was obtained upon photopolymerization by a stronger light source. The phase destruction seems to be reflecting the robustness of the cubic lattice structure against external purterbations.