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Highly efficient twisted nematic liquid crystal polarization gratings achieved by microrubbing Appl. Phys. Lett. 101, 041107 (2012) A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell J. Appl. Phys. 112, 024505 (2012) Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystalsWe have investigated the lasing effect in dye-doped cholesteric liquid crystals, where the photonic stop-band for light propagating along the helical axis coinciding with the layer normal is strongly shifted to longer wavelengths with respect to the luminescence band of the dye. In the absence of overlapping of the photonic and luminescence bands, the well-known lasing effect along the normal at the stop-band edges is forbidden. However, the lasing is still allowed for out-of-normal directions, for which the photonic band is shifted to shorter wavelengths corresponding to the luminescence band. Despite of the out-of-normal light propagation, the positive feedback necessary for the lasing is still available in a case of the monodomain cholesteric layer, when its thickness is much less than the optical pumping aperture. We have observed a significantly increased energy threshold for the out-of-normal lasing modes despite they are characterized by lower threshold gain compared to the modes propagating along the helix axis. The increased energy threshold is explained in terms of continuous distribution of the lasing emission over a large angular sector and energy leakage caused by the leaky lasing into the substrates. V C 2012 American Institute of Physics. [http://dx.

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An investigation was carried out on a hybrid structure consisting of a photosensitive polymer in contact with a nematic liquid crystal (NLC) layer. Before assembling the structure, holographic gratings of different periods were recorded in the photopolymer by two laser beams with opposite circular polarization. Such gratings are known for their unique asymmetric diffraction in case of elliptically polarized light and can be used in optical polarization devices. Due to a spatial modulation of the direction of the local optical axis, the photopolymer modulates the anchoring conditions for NLC in a similar way. As a result, a new grating is induced in NLC with the enhanced diffraction efficiency (in a particular experiment it was four orders of magnitude higher than that of the photopolymer). The NLC grating also shows the characteristic asymmetric diffraction for the reconstructing beams of opposite circular polarizations. The diffraction efficiency is easily controlled by an external electric field.

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