Stable Selective Gratings in LC Polymer by Photoinduced Helix Pitch Modulation

作者：Ryabchun Alexander^*; Bobrovsky Alexey; Gritsai Yuri; Sakhno Oksana; Shibaev Valery; Stumpe Joachim

来源：ACS Applied Materials & Interfaces, 2015, 7(4): 2554-2560.

DOI：10.1021/am507499p

• liquid crystalline polymer
• cholesteric phase
• polarization grating
• phototunable helix pitch
• selective light reflection

A cholesteric mixture based on the nematic liquid crystalline side-chain polymer doped with a chiral-photochromic compound was prepared and used as an active medium for creation of stable polarization selective gratings by phototunable modulation of the helix pitch. Such modulation was fabricated in the polymer mixture by a nonpolarized UV-irradiation with spatially modulated intensity that causes EZ isomerization of a chiral-photochromic dopant, decreasing its helical twisting power. It was shown that the gratings recorded by UV-exposure through a mask are strongly selective to the handedness of circular polarized light. The studied polymer film forms a right-handed helical structure and, correspondingly, the diffraction of only the right-circularly polarized light was found in the transmittance mode. The maximum diffraction efficiencies were found for the wavelength values between the maxima of selective light reflection. The films obtained open very interesting possibilities for further development of materials with stable gratings operating in the entire visible spectral range. Both the position and the width of the spectral range of an efficient diffraction can be easily controlled by the UV exposure and concentration of the dopant. The materials obtained and methods developed can be used for creation of specific diffraction elements for optics and photonics.

• 出版日期2015-2-4