Abstract
Chiral nematic liquid crystals (CLCs) offer interesting perspectives for device applications and are fascinating materials to study because of their ability to self-assemble into complex structures. This work demonstrates that narrow lines of electron-beam resist on top of an ITO coated glass surface can dramatically influence the formation and growth of short pitch chiral superstructures in the bulk. By applying a voltage to the cell, directional growth of CLC structures along the corrugated surface can be controlled. Below the electric unwinding threshold, chiral structures start to grow along the grating lines with their helical axis parallel to the substrates. This results in a uniform lying helix-like structure at intermediate voltages and a chiral configuration with periodic undulations of the helical axis at low voltages.
Highlights
Electro-optic devices that modulate the properties of light have become indispensable in our daily lives since they are the enabling components in displays, cameras, lasers, LEDs, etc
The critical field for dielectric unwinding Ec of Chiral nematic liquid crystals (CLCs) was derived by Kahn [28]: EC
When we look into more detail at the polarizing optical microscopy (POM) images at low voltages, we observe perturbations in the structure (Fig. 3 and Fig. 4)
Summary
Electro-optic devices that modulate the properties of light have become indispensable in our daily lives since they are the enabling components in displays, cameras, lasers, LEDs, etc. In chiral nematic liquid crystal (CLC) the constituent mesogens are chiral, leading to a periodic rotation of the director over a macroscopic length scale. The selforganization of CLC in a helical superstructure gives rise to material properties that are unachievable with achiral LC, such as the existence of a selective reflection band for light with circular polarization corresponding to the handedness of the CLC [6]. This makes especially short pitch CLC, with a reflection band in the visible wavelength range, very interesting for application in tunable lasers, reflective displays, diffraction gratings, etc
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