Search

We have demonstrated a Liquid crystal (LC) analog phase modulator based on the flexoelectric-optic effect that can achieve full 2π phase modulation with sub-millisecond switching speed. The LC mixture in the device consists of the bimesogen CBC7CB with chiral dopant R5011 that can exhibit ±𝜋/4 rotation of the optic axis for an electric field of ±4.2Vμm^(-1). This is then converted to a ±π phase modulation with the aid of a chiral reflector and a quarter waveplate. The residual amplitude modulation is found to be very low, and we show how these elements can be combined to form a integrated device.

Electrical tuning of photonic bandgap (PBG) of cholesteric liquid crystal (CLC) without deformation within the entire visible region at low voltages is not easy to achieve. This study demonstrates low-voltage-tunable PBG in full visible region with less deformation of the PBG based on smart materials of ferroelectric liquid crystal doped CLC (FLC-CLC) integrating with electrothermal film heaters. Experimental results show that the reflective color of the FLC-CLC can be low-voltage-tuned through entire visible region. The induced temperature change is induced by electrically heating the electrothermal film heaters at low voltages at near the smectic-CLC transition temperature. Coaxial electrospinning can be used to develop smart fibrous devices with FLC/CLC-core and polymer-shell which color is tunable in full visible region at low voltages.

The scientists in the field of liquid crystal (LC) have paid significant attention in the exploration of novel cholesteric LC (CLC) polymer template (simply called template) in recent years. The self-assembling nanostructural template with chirality can effectively overcome the limitation in the optical features of traditional CLCs, such as enhancement of reflectivity over 50%, multiple photonic bandgaps (PBGs), and changeable optical characteristics by flexibly replacing the refilling LC materials, and so on. This work fabricates two gradient-pitched CLC templates with two opposite handednesses, which are then merged as a spatially tunable and highly reflective CLC template sample. This sample can simultaneously reflect right- and left-circularly polarized lights and the tunable spectral range includes the entire visible region. By increasing the temperature of the template sample exceeding the clearing point of the refilling LC, the light scattering significantly decreases and the reflectance effectively increase to exceed 50% in the entire visible region. This device has a maximum reflectance over 85% and a wide-band spatial tunability in PBG between 400 nm and 800 nm which covers the entire visible region. Not only the sample can be employed as a wide-band spatially tunable filter, but also the system doping with two suitable laser dyes which emitted fluorescence can cover entire visible region can develop a low-threshold, mirror-less laser with a spatial tunability at spectral regions including blue to red region (from 484 nm to 634 nm) and simultaneous lasing emission of left- and right-circular polarizations.

This study elucidates electrically and all-optically controllable random lasers in dye-doped liquid crystals with adding a photoisomerizable dye. The lasing intensities and the energy thresholds of the random lasers can be electrically controlled below the Freedericksz transition threshold or all-optically controlled sequentially with a two-step exposure of UV and green beams. The below-threshold-electric- and all-optical controllabilities of the random lasers are attributable to the effective change of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by changing the electric-field-aligned order of LCs below the threshold and via the isothermal nematic-isotropic phase transition of LCs, respectively; thereby changing the diffusion constant and thus the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the change in the lasing intensity and thus the energy threshold of the random lasers.