Tri-Stable Polarization Switching of Fluorescent Light Using Photo-Luminescent Cholesteric Liquid Crystals

Abstract

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.

Photonic Bandgap–Cholesteric Device with Electrical Tunability and Optical Tristability in Its Defect Modes

“…The optical transparency of the ULH is comparable to that of the homeotropic (H) state in that it can be regarded as a uniaxial crystal. To date, possible applications of this tristable CLC have been suggested for the switchable reflector in a transflective display [20], and the optical switch for the control of the polarization of fluorescent light [21]. In this study, we focus on the driving scheme for textural switching among the stable P, FC and the ULH states, and present a tristable 1D PC/CLC device based on their spectral features.…”