Electrically Switchable Asymmetrical and Anisotropic Light Scattering by Polymer Network 90° Twisted Nematic Liquid Crystals
Ko-Ting Cheng1*, Wei-Hsuan Chen1, Cheng-Kai Liu1
1Department of Optics and Photonics, National Central University, Taoyuan City, Taiwan
* Presenter:Ko-Ting Cheng, email:chengkt@dop.ncu.edu.tw
Polymer network 90° twisted nematic liquid crystals (PN-90° TNLCs) are usually considered to work as optically isotropic scattering-type light shutters. It indicates that the incident lights with their propagation directions perpendicular to the substrates from both directions (±z-axis), will be identically scattered. Here, the properties of electrically switching, asymmetrical and anisotropic scattering, and their applications of PN-90° TNLCs are reported. Briefly, the doped reactive mesogen will be polymerized and aligned along 90° TNLCs. LC alignment can continuously rotate from one substrate to the other. Accordingly, the generated polymer network structures will be consistent with that of the 90° TNLCs. Without the application of external voltage, PN-90° TNLCs work as common 90° TNLCs. However, with suitable external voltage application, regarding the asymmetrical scattering, incident lights with a specifically linear polarization direction can penetrate PN-90° TNLCs from one direction; the linearly polarized light, which comes from the opposite direction, can be scattered. The reason for such light scatterings results from the refractive index mismatch of the generated multi LC domains. Moreover, regarding the anisotropic scattering, one of two orthogonal linearly polarized light can be scattered by the PN-90° TNLCs with application of suitable voltage. Such LC devices can be adopted as an electrically switchable scattering-type linear polarizers and optical isolators. They are believed to have great potentials for display and information technologies.

Keywords: Liquid crystals, Polymers, Scattering