PHOTOALIGNMENT OF LIQUID CRYSTALS: APPLICATIONS TO FAST RESPONSE FERROELECTRIC LIQUID CRYSTALS AND REWRITABLE PHOTONIC DEVICES

Photoalignment of liquid crystals by using azo dye molecules is a commonly proposed alternative to traditional rubbing alignment methods. Photoalignment mechanism can be well described in terms of rotational diffusion of azo dye molecules exposed by ultraviolet polarized light. A specific feature of the irradiated light is the intensity dependent change of azimuthal anchoring of liquid crystals. While there are various mechanisms of azo dye photoalignment, photo-reorientation occurs when dye molecules orient themselves perpendicular to the polarization of incident light. In this review, we describe both recent achievements in applications of photoaligned liquid crystal cells and its simulation. A variety of display and photonic devices with azo dye aligned nematic and ferroelectric liquid crystals are presented: q-plates, optically rewritable flexible e-paper (monochromatic and color), and Dammann gratings. Some theoretical aspects of the alignment process and display simulation are also considered.

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Photo-Aligned Ferroelectric Liquid Crystal Devices with Novel Electro-Optic Characteristics

Crystals ◽

10.3390/cryst10070563 ◽

2020 ◽

Vol 10 (7) ◽

pp. 563

Author(s):

Vladimir Chigrinov ◽

Qi Guo ◽

Aleksey Kudreyko

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Berry Phase ◽

Photonic Devices ◽

Ferroelectric Liquid Crystal ◽

Optical Elements ◽

Ferroelectric Liquid Crystals ◽

Liquid Crystal Devices ◽

Alignment Technique ◽

Photo Alignment

This paper examines different applications of ferroelectric liquid crystal devices based on photo-alignment. Successful application of the photo-alignment technique is considered to be a critical breakthrough. A variety of display and photonic devices with azo dye aligned ferroelectric liquid crystals is presented: smart glasses, liquid crystal Pancharatnam–Berry phase optical elements, 2D/3D switchable lenses, and laser therapy devices. Comparison of electro-optical behavior of ferroelectric liquid crystals is described considering the performance of devices. This paper facilitates the optimization of device design, and broadens the possible applications in the display and photonic area.

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Ferroelectric Liquid Crystals: Physics and Applications

Crystals ◽

10.3390/cryst9090470 ◽

2019 ◽

Vol 9 (9) ◽

pp. 470 ◽

Cited By ~ 10

Author(s):

Guo ◽

Yan ◽

Chigrinov ◽

Zhao ◽

Tribelsky

Keyword(s):

Liquid Crystals ◽

High Resolution ◽

Contrast Ratio ◽

Fast Response ◽

High Contrast ◽

Ferroelectric Liquid Crystals ◽

Electrooptic Effects ◽

Potential Applications ◽

Anchoring Energy ◽

General Operation

Electrooptic modes with fast response and high contrast ratio are highly desirable in modern photonics and displays. Ferroelectric liquid crystals (FLCs) are especially promising for fulfilling these demands by employing photoalignment technology in FLC cells. Three electrooptic modes including surface stabilized FLC (SSFLC), deformed helix ferroelectric (DHF) mode, and electrically suppressed helix (ESH) mode are reviewed with the corresponding electrooptic effects like bi- and multi-stable switching, continuous modulation of grayscale or phase, and high contrast switching. The general operation principles FLC electrooptic modes are described, and then the characteristics of each modes for potential applications are summarized. With the advantages of controllable anchoring energy, the photoalignment provides FLC samples with uniform alignment and high contrast ratio. The fast FLCs with a high resolution and high contrast can be used in the next generation display including field sequential color FLC microdisplays, as well as switchable 2D/3D televisions.

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