Tri-stable polarization switching of fluorescent light using photo-luminescent cholesteric liquid crystals

Using a photo-luminescent cholesteric liquid crystal (PL-CLC) cell, tri-stable electrooptic switching behaviour was demonstrated. Stable planar, uniformly lying helix (ULH), and focal conic states were obtained at an electric field of zero after applying proper electric signals corresponding to each state. When a PL-CLC cell was placed on a ultraviolet (UV) back-light, the cell emitted fluorescent light with different types of polarization corresponding to the liquid crystal (LC) state: the planar, ULH, and focal conic states emitted circularly polarized light, linearly polarized light, and un-polarized light, respectively. Hence, the proposed PL-CLC cell worked as a tri-stable polarizationswitching light source. We also demonstrated that the PL-CLC cell can be used to fabricate a bistable fluorescent LC device.