Abstract

The phenomenon of athermal, light-field-induced pitch dilation of a cholesteric liquid crystal (CLC) helix under conditions of selective Bragg reflection of circularly polarized light has been theoretically predicted in Ref.[1]. As one consequence of this pitch dilation, a change in reflectivity of the CLC was predicted. In experiments, however, e.g. [2,3] only thermally driven changes in selective reflection have been observed in absorbing CLCs. The authors of Ref. [4], using pure CLCs and short laser pulses (15 ns), were unable to detect any reflectivity changes in accordance with Ref. [1], due to driving field strengths E not exceeding the threshold value of ~10⁴ V/cm over the time interval of the helix untwisting T, i.e. several ms. There exists only one set of literature reports [5], in which changes in the curvature of CLC mirrors were traced to pitch dilation in the field of a light wave, but no corresponding changes in reflectivity were reported.

© 1996 IEEE