Optical pattern formation is usually due either to the combination of diffraction and nonlinearity in a Kerr medium or the temporal modulation of light in a photosensitive chemical reaction. We present a different mechanism by which light spontaneously induces stripe domains between nematic states in a twisted nematic liquid crystal layer doped with azo-dyes. Due to the photoisomerization process of the dopants, light creates dissipative structures without the need of temporal modulation, diffraction, Kerr or other optical nonlinearity, but based on the different scales for dopant transport processes and nematic order parameter, which identifies a Turing mechanism for this instability. Theoretically, the emergence of the stripe patterns is described by a model for the dopant concentration coupled with the nematic order parameter.

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Marcel G. Clerc, "Spontaneous light-induced Turing patterns in a dye-doped twisted nematic layer: Theory and experiments (Conference Presentation)," Proc. SPIE 10735, Liquid Crystals XXII, 107350M (Presented at SPIE Organic Photonics + Electronics: August 20, 2018; Published: 18 September 2018); https://doi.org/10.1117/12.2319213.5836581507001.