Abstract
We studied the appearance of second- and third-order Bragg reflections in cholesteric liquid crystals (CLCs) in cells where the electric field was perpendicular to the helical axis. Second-order reflections with reflectance values as large as 80% of the first-order one were observed in the gap regions of alignment cells with interdigitated electrodes for CLC mixtures with pitches in the range 0.5-1.0 μm upon application of a field. The characterization was enabled by local probing of the CLC using a microspectrophotometer. LC cells that are transparent in the visible spectrum in the off-state and become colored upon application of a field due the second- or third-order reflection band appearance were demonstrated. The spectral position of the higher-order Bragg reflections can also be tuned by adjusting the magnitude of the electric field.
Highlights
In cells with interdigitated electrodes (IDEs), the electric field is not uniform when a potential difference is applied between the two sets of electrodes
Because the response of a cholesteric liquid crystal (CLC) material to applied electric fields depends on the direction and strength of the field, the electro-optic response in this type of cell can be complex
Our main focus has been the monitoring of the helix unwinding for CLCs with positive dielectric anisotropy in regions of the cells between the electrodes, where the electric field is in the plane of the substrate and perpendicular to the helical axis
Summary
In cells with interdigitated electrodes (IDEs), the electric field is not uniform when a potential difference is applied between the two sets of electrodes.
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