Liquid crystalline blue phases show excellent potential for application in tunable photonic devices because they possess a unique optical property: their the selective 3D Bragg diffraction in a visible wavelength region can be continuously shifted by using an electric field. However, to take full advantage of this potential, a new approach to simultaneously extend the wavelength range of field-induced Bragg diffraction shift and the temperature range of thermodynamically stable BPs is critically needed.
Now, a group from Kyushu University in Japan have successfully developed a new BP material system using a dendron molecule to extend simultaneously the two blue phase ranges. The first is the temperature range of thermodynamically stable BPs, which they expanded from 2.1 oC to 4.6 oC. The second is the reversible maximum shift range of Bragg wavelength on the electric field, which has been extended from 85 nm to 109 nm. They have also explored the physical mechanism of the dendron-stabilizing effect in BPs, and discuss it in terms of elastic properties and the orientational order of the liquid crystal molecules.