Liquid crystal depolarizer based on photoalignment technology

We propose a depolarizer based on the principle of a collection of half-wave plates with randomly distributed optic axes. The design is demonstrated by means of dynamically photopatterning liquid crystal into randomly aligned homogeneous domains. We characterize the liquid crystal depolarizer for 1550 nm and C-band(1520–1610 nm). A degree of polarization of less than 5% is obtained for any linearly polarized light. This study provides a practical candidate for high-performance depolarizers.

DESIGN AND STUDY OF NEW AZOBENZENE LIQUID CRYSTAL/POLYMER MATERIALS

Discussion is presented on the use of the photoisomerization of azobenzene chromophore in the design andpreparation of novel functional materials. The two systems reviewed are azobenzene polymer-stabilized liquid crystals andazobenzene elastomers. In the first case, a polymer network containing azobenzene moieties is used to optically induce andstabilize a long-range liquid crystal orientation without the need of treating the surfaces of the substrates. This optical andrubbing-free approach was applied to nematic and ferroelectric liquid crystals. In the second case, an azobenzene side-chainliquid crystalline polymer is grafted onto a styrene-butadiene-styrene triblock copolymer to yield a photoactive thermoplasticelastomer. Coupled mechanical and optical effects make possible the formation of dimaction gratings that may be useful formechanically tunable optical devices.

Increasing the rewriting speed of optical rewritable e-paper by selecting proper liquid crystals

The effect of interaction between liquid crystal （LC） and photoalignment material on the speed of optical rewriting process is investigated. The theoretical analysis shows that a smaller frank elastic constant K22 of liquid crystal corresponds to a larger twist angle, which gives rise to a larger rewriting speed. Six different LC cells with the same boundary conditions （one substrate is covered with rubbed polyimide （PI） and the other with photo sensitive rewritable sulfuric dye I（SD1）） are tested experimentally under the same illumination intensity （450 nm, 80 mW/cm2）. The results demonstrate that with a suitable liquid crystal, the LC optical rewriting speed for e-paper application can be obviously improved. For two well known LC materials E7 （K22 is larger） and 5CB （K22 is smaller）, they require 11 s and 6 s corresponding to change alignment direction for generating image information.

Dual photopatterning of rotational fingerprint superstructures

Controlling architecture of hierarchical microstructures in liquid crystals(LCs]plays a crucial role in the development of novel soft-matter-based devices.Chiral LC fingerprints are considered as a prospective candidate for various applications;however,the efficient and real-time command of fingerprint landscapes still needs to be improved.Here,we achieve elaborate rotational fingerprint superstructures via dual photopatterning semifree chiral LC films,which combine the photoalignment technique and a dynamic light patterning process.An intriguing spatial-temporal rotational behavior is presented during the patterning of chiral superstructures.This work opens new avenues for the applications of chiral LCs in soft actuators,sensing,and micromanufacturing.

High damage threshold liquid crystal binary mask for laser beam shaping

In order to improve the damage threshold and enlarge the aperture of a laser beam shaper, photolithographic patterning technology is adopted to design a new type of liquid crystal binary mask. The inherent conductive metal layer of commercial liquid crystal electro-optical spatial light modulators is replaced by azobenzene-based photoalignment layers patterned by noncontact photolithography. Using the azobenzene-based photoalignment layer, a liquid crystal binary mask for beam shaping is fabricated. In addition, the shaping ability, damage threshold, write/erase flexibility and stability of the liquid crystal binary mask are tested. Using a 1 Hz near-IR(1064 nm) laser, the multiple-shot nanosecond damage threshold of the liquid crystal mask is measured to be higher than 15 J/cm^2. The damage threshold of the azobenzenebased photoalignment layer is higher than 50 J/cm^2 under the same testing conditions.

Circular Airy beams realized via the photopatterning of liquid crystals[Invited]

The generation of an autofocusing circular Airy beam(CAB)is realized via a liquid crystal(LC)geometric phase plate with a simple configuration.The fabrication of the LC plate is based on the photoalignment technology and dynamic exposure skill.A focal length of 74 cm is obtained,and the propagation dynamics are consistent with the simulations.Besides,a defocusing CAB is also generated,and the switch between the autofocusing and defocusing CABs can be achieved by controlling the input polarization state.This work provides a convenient and flexible approach to acquire CABs,which will promote the CAB-related applications and researches.