Photoinduced two-dimensional gratings based on dye-doped cholesteric liquid crystal films

Hui-Chen Yeh; Guang-Hao Chen; Chia-Rong Lee; Ting-Shan Mo
October 2007
Journal of Chemical Physics;10/14/2007, Vol. 127 Issue 14, p141105
Academic Journal
This work elucidates photoinduced two-dimensional (2D) gratings in dye-doped cholesteric liquid crystal films. The helical pitch is increased by green-beam-induced trans-cis isomerization and a concomitant thermal effect. Two-dimensional gratings appear when the green beam is turned off. Grating formation results from elastic instability caused by restored strain arising from helical pitch reduction. Grating lifetime increases as green beam intensity increases and declines under irradiation with a strong red beam. Variation in grating spacing with green intensity with various pitches is also examined.


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