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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Control of topological defects in microstructured liquid crystal cells
Optics Express
|June 5, 2009
Summary
We demonstrate active tuning of light propagation in micro-structured cells by controlling nanoscale defects in liquid crystals. Defect motion within these cells enables faster optical symmetry changes than in planar cells.
Area of Science:
- Optics and Photonics
- Materials Science
- Soft Matter Physics
Background:
- Micro-structured cells offer novel ways to control light propagation.
- Nematic liquid crystals (NLCs) exhibit unique optical properties influenced by molecular alignment and defects.
- Nanoscale defects in NLCs can be manipulated by external fields.
Purpose of the Study:
- To investigate the active tuning of light propagation in 'planar-spherical' micro-structured cells.
- To understand the role of nanoscale defects in NLCs within these cells.
- To compare the dynamics of defects in micro-structured cells versus traditional planar cells.
Main Methods:
- Fabrication of 'planar-spherical' cells comprising a planar and a gold-coated hemispherical micro-mirror.
- Optical reflection imaging of back-reflected polarized light.
- Application of voltage to induce and observe defect motion.
- Theoretical modeling of NLC alignment and defect formation.
- Experimental measurement of relaxation times for back-reflected intensity.
Main Results:
- Observed a remarkable change in the symmetry of back-reflected polarized light with applied voltage.
- Theoretical models confirmed that cell geometry and electric fields induce defect formation and motion.
- The motion of these defects directly correlates with the observed changes in optical symmetry.
- Experimental data showed significantly faster defect motion in micro-structured cells compared to planar cells.
Conclusions:
- Active tuning of light propagation is achievable in micro-structured cells by manipulating nanoscale liquid crystal defects.
- The unique geometry of 'planar-spherical' cells facilitates faster defect dynamics.
- These findings open possibilities for advanced optical devices with tunable properties.
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