Chiral liquid crystal phases are fascinating materials with unique optical and structural properties that make them attractive for various technological applications. Understanding the mechanisms behind their structure transformation, deformation, and optical properties is crucial for their successful implementation in devices. Moreover, creating a mono-domain blue-phase liquid crystal is of great interest due to its potential for high-speed display applications. In this talk, I would like to introduce LC phases with periodic helical structures, induced by adding chiral molecules into the nematic phase. By changing the chirality and temperature, we can obtain one-dimensional and three-dimensional periodic helical structures. When the periodic helical structures and the wavelength of the incident light are satisfied with Braggs' reflection condition, the helical LCs reflect various visible colors. The attractive thing is that the reflection and of them can be tunable in many ways easily. For 3-D helical LC, called blue-phase liquid crystal, the tunable reflection band comes from the lattice deformation and matainsites transformation, checked by lattice diffraction.
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