Abstract
Two types of cholesteric liquid crystal (CLC) fingerprint structures, namely developable-modulation (DM) and growing-modulation (GM), can be contemporaneously prepared in polymer stabilized CLC (PSCLC) composites, to be mutually perpendicular in a repeatable and reversible voltage-switching process when the cell thickness to pitch length ratios (d/P) were appropriately chosen. PSCLC grating structures with interlaced DM/GM fingerprint textures were achieved by varying the applied voltage and sequentially photopolymerizing the dissolved mesogenic monomers through photomasks with stripe and checker patterns. The morphologies of the distinct interlaced PSCLC structures via different UV exposure sequences were investigated under crossed polarizing optical microscopy (POM) and scanning electron microscopy (SEM). The optimized results suggest that DM gratings should be stabilized before GM gratings. Diffraction measurements reveal polarization-dependent properties of the interlaced DM/GM gratings. The intensity redistribution of diffraction orders in orthogonal direction can be achieved by changing the polarization state of incident laser beam.
Highlights
The cholesteric liquid crystals (CLCs) media, possessing a unique supramolecular helical structure, has become a subject of great scientific attention for beyond-display applications, such as mirrorless band-edge lasers [1], hyper-reflectors [2], optical sensors [3], light modulators [4], and so on [5,6,7,8,9,10]
The direction of cholesteric grating vectors is determined by the director direction of CLC molecules in the middle layer, which is mutually perpendicular between the planar and the transition planar zone [8, 31]
We demonstrate a flexible method to stabilize different types of interlaced DM/GM fingerprint textures in the same cell by means of sequential photopolymerization of CLCs doped with reactive mesogenic monomer
Summary
The cholesteric liquid crystals (CLCs) media, possessing a unique supramolecular helical structure, has become a subject of great scientific attention for beyond-display applications, such as mirrorless band-edge lasers [1], hyper-reflectors [2], optical sensors [3], light modulators [4], and so on [5,6,7,8,9,10]. The mesogenic monomers dissolved in CLCs are photo-polymerized in the fingerprint state These networks provide anchoring capabilities which maintain the liquid crystalline order in bulk and do not seriously interrupt the morphology of the CLC system. These polymer-stabilized CLC gratings (PSCLCs) can operate in the absence of an applied electric field and exhibit a millisecond-scale response to low voltage in either the Bragg or Raman-Nath limits. The optimized results suggest that the polymerization of DM type fingerprint texture should be prior to that of GM texture to preserve the structural integrity These distinct interlaced helical superstructures were based on polymer stabilized CLCs and the polarization-dependent properties were investigated by the diffraction measurements
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