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Fabrication and Characterization of Polymer/Liquid Crystal Composite Diffractive Optics by Multiphoton Methods
Author(s) -
Xie A.,
Ito T.,
Higgins D. A.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600575
Subject(s) - materials science , liquid crystal , indium tin oxide , diffraction , optics , homeotropic alignment , microscopy , optoelectronics , polymer , photolithography , polarization (electrochemistry) , nanotechnology , composite material , thin film , physics , chemistry
Direct‐write multiphoton photolithography is used to prepare electrically switchable diffraction gratings having spacings as small as 4 μm. Surface‐relief gratings are written into poly(methyl methacrylate) films using a sample‐scanning confocal microscope and are characterized by using contact‐mode atomic force microscopy. The resulting polymeric channels are filled with nematic liquid crystals (LCs) and sandwiched between indium tin oxide‐coated coverslips to obtain functional devices. These devices exhibit diffraction efficiencies approaching 30 %. Microscopic LC organization and field‐induced reorientation dynamics within these devices are characterized by static and dynamic polarization‐dependent multiphoton excited fluorescence microscopy. LCs are found to align predominantly along the channel axis, but exhibit some disorder near the channel walls, resulting from nanometer‐scale polymer surface roughness. LC reorientation in response to an electric field is rapid (<1 ms) and uniform, whereas field‐free LC relaxation is relatively slow (>20 ms). Both reorientation and relaxation are influenced by orientationally anchored LCs near the channel walls.