Open AccessTime-domain analysis of optically controllable biphotonic gratings in azo-dye-doped cholesteric liquid crystals
Author(s) -
H. C. Yeh
Publication year - 2011
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.005500
Subject(s) - materials science , optics , cholesteric liquid crystal , liquid crystal , elongation , photoisomerization , isomerization , polarization (electrochemistry) , irradiation , doping , beam (structure) , circular polarization , optoelectronics , photochemistry , chemistry , physics , biochemistry , nuclear physics , ultimate tensile strength , catalysis , microstrip , metallurgy
This study investigated optically controllable biphotonic gratings (BGs) in azo-dye-doped cholesteric liquid crystals. The BGs were formed under the illumination of one green beam with the simultaneous irradiation of an interference field generated by two coherent red beams. This study ascribes the formation of the BGs to the green-beam-induced dye reorientation and elongation of the helical pitch through trans-cis isomerization and red-beam-induced suppression of dye reorientation and elongation of the helical pitch by cis-trans back isomerization. The diffraction characteristics strongly depended on the helical pitch of the cholesteric structure, the polarization state of the probe beam, and the relative intensity of the green and red beams. Application of the finite-difference time-domain method demonstrated that the model of photoinduced distortion of the cholesteric liquid crystal structure satisfactorily explains this dependence.