Nano-dimensional short pitch ferroelectric liquid crystal materials and devices with improved performance at oblique incidence

摘要

Deformable Helix Ferroelectric Liquid Crystal (DHFLC) devices with nanodimensionally short pitch are examined for the purpose of applications in biomedical optical imaging. While nematic Liquid Crystal (NLC) devices have been used in our previous research as retarders, optical filters and polarization rotators and integrated into biomedical optical imaging systems, the current research is devoted to DHFLCs and to highlight the advantages that these devices can offer. Ferroelectric Liquid Crystal (FLC) devices are considerably faster than Nematic LC devices, the DHFLC sub group possesses other, more desired effects. The desired electro-optical response of the device is continuous, hysteretic-free and insensitive to the sign of the applied voltage. This can be achieved by using the DHFLC V-shaped switching effect which is observed when the helix pitch magnitude is shifted to nanoscale below 400nm (sub-wavelength) down to 150 nm. DHFLC cells with a sub-wavelength helix pitch have small light scattering in the visible spectral range when the applied voltage is below the critical level of the helix unwinding. Designs, experimental results and simulations are presented particularly for the reflectivity at oblique incidence showing some unique properties including polarization independent modulation, faster response and surface waves excitation.