Abstract: High-intensity circular polarized light beams tuned to selective-reflection condition in ultra-pure cholesteric liquid-crystal layer made possible observation of athermal light-induced drop in the chiral reflection coefficient of liquid-crystal layer. The dependence of the effect on intensity (not on average power) permits one to connect it mechanistically with the chiral CLC helix pitch dilation up to spiral untwisting. Under the current, specifically chosen experimental irradiation conditions, nonlinear bleaching of the medium's reflectivity could be observed over time intervals that allow a distinction in the driving mechanism of nonlinear bleaching between optical-field-induced and thermal effects. The effect was observed both in free space and inside laser resonator, where CLC layer was used as end mirror.!7
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