We report a room-temperature dual-frequency field assembly technique that is capable of fabricating large-areal size (~cm2 or larger), well-aligned cholesteric liquid crystals to thicknesses up to 2.2 mm, corresponding to period number N (thickness/index grating period) of nearly10,000 in the visible spectral regime. The method employs successive application of low- and high- frequency electric field on a thick cell of CLC starting mixture containing a nematic constituent of negative anisotropy. The low-frequency field creates conductive hydrodynamical instabilities that mash the mixture to a state with completely randomized orientation of the cholesteric helices; the next application of a high-frequency field at a field strength below the dielectric hydrodynamic instability reorient all the helices into uniform standing helices. Such extraordinarily thick chiral photonic crystals exhibit many never-before-realized chiral photonic properties such as giant rotation of optical polarization with high transmission (low scattering loss), polarization switching and ultrafast pulse modulation capabilities for visible to mid-infrared lasers, in addition to dynamic tunability by electrical, thermal, or optical means.
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