V.G. Chigrinov

Hong Kong University of Science and Technology | UST · Department of Electronic and Computer Engineering

Properties of surface anchoring depend on the absorbed exposure energy and various potential interactions associated with liquid crystal and azo dye layers. In this study, we investigate a model of dispersion, steric and photoinduced interactions with the goal of providing a qualitative and quantitative description of orientationally ordered hard u...

Photoalignment by azo dye nanolayers can provide high alignment quality for large-area liquid crystal devices. Application of this technology to active optical elements for signal processing and communications is a hot topic of photonics research. In this article, we review recent demonstrations and performance of liquid crystal photonic devices, d...

Interactions between liquid crystal molecules and target analytes open up various biosensing applications for quick screening and point-of-care applications. In this review, we categorized biosensors by type, depending on the liquid crystal mesophase, and considered several applications for the detection of biomolecules, point-of-care diagnostics a...

In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper are reported. The possible production of Digital Mirror Devices and the roll-to-...

With the advancement of information display technologies, research on liquid crystals is undergoing a tremendous shift to photonic devices. For example, devices and configurations based on liquid crystal materials are being developed for various applications, such as spectroscopy, imaging, and fiber optics. One of the problems behind the developmen...

Optical security films have gained a lot of attention due to its potential application in authentication services. Electrode-free optical devices are in demand along with electrode devices due to its secure access to the decryption key and ability to hide information from public access. Our concern in this study is the examination of electrode-free...

The ability to establish significant phase modulation at low applied field provides a promising route toward polarization control and wavefront shaping for liquid‐crystal‐based devices. Owing to the polarization‐selective reflectivity of chiral liquid crystals (CLCs), reflective wavefront shaping via geometric phase is demonstrated when a circularl...

Time-limited exposure of electrode-free optically rewritable electronic paper is essential for applications, but performance characteristics can be modest. In this study, we investigate whether image writer mode can improve kinetics of the photosensitive layer order parameter, which is described by the rotational diffusion model. The model that we...

This chapter focuses on the progress in developing bistable Optically Rewritable Liquid Crystal Display (ORW LCDs) based on photoalignment technology over the past few years. It reviews photoalignment technology, which is essential for understanding ORW technology. The chapter presents the features of ORW LCDs including rewriting speed, gray levels...

A comprehensive theory of light-reflective characteristics and experimental technique of liquid crystal layer thickness control for flexible optically rewritable electronic paper is presented. Cylindrical pillars were used to control the gap between flexible substrates. The introduced prototype of optically rewritable electronic paper has shown ver...

A non‐contact photo‐alignment technology was proposed to align silver nanowires (AgNWs) in a liquid crystal polymer (LCP) film with high order parameter. They are controlled to have planar alignment and twisted nematic structures in micro‐multi‐domains. The aligned AgNWs can be used to improve the mechanical properties of LCP films. The AgNW/LCP fi...

The self‐assembly of silver nanowires (AgNWs) with a high aspect ratio is highly desirable for practical applications; however, several challenges still exist. Herein, a non‐contact, simple, large‐scale, micro‐domain photo‐alignment technology is proposed to align AgNWs in a liquid crystal polymer (LCP) film, resulting in a high order parameter (ab...

We propose a period control method of liquid crystal polarization grating (LCPG) based on an nterference-free and single exposure process. By adjusting three parameters of exposure setup, including incident angle of exposure beam, wedge angle of birefringent prism and tilt angle of the sample, polarization distribution of the exposure beam is chang...

In this review we describe the reversible photoalignment effect imposed on the director in nematic liquid crystals that provides an approach for fabrication of advanced optically addressed devices. Several new concepts have been developed to render photosensitive materials during the past decade. Functional soft azo dye compounds exhibiting distinc...

Photoalignment of liquid crystals with azo dyes has a high potential for display and non-display applications. In this study, we report the existence of abnormal relaxation of photoinduced retardation in azo dye layers. Our results were obtained on the experimental setup, where the phase retardation of azo dye was measured by a photoelastic modulat...

We report a ferroelectric liquid crystal (FLC) compound lens based on the Pancharatnam–Berry (PB) phase. The phase of the FLC compound lens is an integration of polarization grating and a PB lens. Thus, when light passes through an FLC compound lens, the output light’s polarization handedness will be changed accordingly. In this case, FLC compound...

Photoalignment on azo dye films is a simple and efficient way to achieve anisotropic ordering of molecules, which is promising to achieve ultra-thin high-performance dichroic polarizers. Besides, the photoalignment technique shows a unique advantage on patterned alignment applications, and enables the realization of advanced optical elements such a...

Light-reflecting characteristics play a crucial role in optically rewritable liquid crystal display (electronic paper). By using a special optimizer software, light-reflecting characteristics of the twisted nematic cell were calculated. The achieved values of the normalized reflection coefficients range within ∼ 0.03 - 0.43, which is comparable or...

Time-limited exposure of electrode-free optically rewritable electronic paper is essential for applications, but performance characteristics can be modest. In this study we investigate whether image writer mode can improve kinetics of the photosensitive layer order parameter, which is described by the rotational diffusion model. The model that we d...

Recent achievements in the photoalignment technique for fabrication of optically rewritable electronic paper with high performance characteristics are surveyed with emphasis on temporal constraints on the exposure process. The possibility of creating electrode-free electronic paper has very important practical aspects. However, many existing studie...

We report the ferroelectric liquid crystal (FLC) Pancharatnam-Berry lenses (PBLs) with rapid transmittance tunability. The FLC PBLs were fabricated using a single-step holographic exposure system based on a spatial light modulator working as numerous polarization retarders, providing a simple way to fabricate FLC continuous aligning structures. A s...

A period control method of liquid crystal polarization grating is demonstrated, which is based on the polarization modulation of the exposure beam and can be realized by changing the angle parameters in the exposure setup. This method has the advantages in compact structure, high flexibility and good robustness. It provides a new choice for the fab...

The development of novel photoaligned fast ferroelectric LCD based on Deformed Helix Ferroelectric (DHF) and Electrically Suppressed Helix (ESH) mode is discussed. A fast response time and a high contrast ratio in ESH mode was observed. These modes can be successfully used for new FLC applications

Optically rewritable technique based on photoalignment azodye nanolayers technology will be discussed for various applications in labels and plastic card displays, as well as for security applications.

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 c...

An all-solid organic semiconducting conjugated polymer poly(2-methoxy-5-(2ʹ-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV) activated polarisation grating (PG) laser was demonstrated for the first time. The PG structure was fabricated based on photoalignment and stacking of multiple reactive mesogen sublayers to provide distributed feedback, and the...

Reflective liquid crystal displays are attracting attention as portable information systems because of zero- or extremely low power consumption. In this study, we deal with an electrode-free reflective liquid crystal cell, where image formation is achieved by coating one of the substrates with optically active azo dye thin film. To describe reflect...

Composite materials containing liquid crystalline microstructures, providing fast stimuli responsive variations of birefringence at low consumption power, have great potential applications in photonics. Here, a composite material based on polymer membranes with photo-aligned nematic microstructures is proposed for the first time. For this purpose,...

The authors have presented a method of ultrasonic intensification of anode–cathode interactions during the formation, in water–alkali electrolytes, of ceramic-like coatings on the surface of valve metals in the process of low-temperature plasma synthesis. An algorithm of directional influence of high-energy fields on the distinctive features and ra...

Photoalignment materials can be effectively used in LC alignment and patterning for new generations of LC devices with extremely high resolution and optical quality both in glass and plastic substrates. Ferroelectric Liquid Crystals based on photoalignment are very promising for new display and photonics devices.

Optically driven liquid crystal displays (ODLCDs) realizes their display function by tuning the easy axis of liquid crystal (LC) molecules under polarized blue light, which has been utilized in some optical devices due to its advantages of ultra-low power consumption. However, a big issue arises in response time, i.e., the rewriting time of the ODL...

Diffractive optical elements attract a considerable amount of attention, mainly due to their potential applications in imaging coding, optical sensing, etc. Application of ferroelectric liquid crystals (FLCs) with photoalignment technology in diffractive optical elements results in a high efficiency and a fast response time. In this study we demons...

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 Pan...

Objectives . Since the end of the 20th century, liquid crystals have taken a leading position as a working material for the display industry. In particular, this is due to the advances in the control of surface orientation in thin layers of liquid crystals, which is necessary for setting the initial orientation of the layer structure in the absence...

We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3...

The optically driving liquid crystal displays (ODLCDs), by changing the easy axis of liquid crystal molecules under exposure light, are exploited in many display devices requiring ultra-low consumption. In this manuscript, we propose foldable and bendable colour ODLCDs lacking electronics and common back light. Two techniques to realise colour ODLC...

Orbital angular momentum (OAM) of light has been extensively studied during the past two decades. Till now, it is a formidable challenge to dynamically manipulate OAM in fast switching speed, good beam quality and low power consumption. Here, an alternative strategy is proposed through the combination of the uniformly-aligned ferroelectric liquid c...

An approach for generating cycloidal pattern of liquid crystal (LC) molecules based on interference-free and single exposure is illustrated. The spatial manipulation of polarization state is achieved using birefringent prism and wave plates. And then, the spatially variant polarization of exposure beam is transferred to LC molecules by azo-dye phot...

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 ferroel...

Mixing liquid crystal with chiral dopant for increasing the response speed of optical driving liquid crystal display was investigated in this paper. It is demonstrated that by adding chiral dopant, rewriting time could be decreased from 30 s to 20 s with good repeatability. Without adding other steps in the process of making cells, this improvement...

The ferroelectric liquid crystal (FLC) which has the advantage of a fast response under an electrical field has become one of the most promising candidates of the next generation liquid crystal display (LCD) as well as photonic devices. In the display area, sub‐millisecond switching is needed to enable field sequential color (FSC) display technolog...

Dual-frequency liquid crystal materials are used in fast response electrooptic modulators in different devices for digital information displaying and processing. In an NLC mixture 2f-3333 (ROLIC, Switzerland) there are components with lateral dipole moment. Their molecular relaxation is investigated by a method of dielectric spectroscopy. Values of...

In this article, we disclose a field sequential color display based on the vertically aligned deformed helix ferroelectric liquid crystals (VADHFLCs) with enhanced Kerr constant (KKerr). The KKerr for VADHFLCs strongly depends on the pitch (p0) and spontaneous polarization (Ps) of the ferroelectric liquid crystal (FLC) material. The longer pitch re...

Holographic lithography is widely used as an effective approach for two-dimensional (2D) photonic crystal fabrication. However, for the fabrication of 2D polarization structures based on photoaligned liquid crystals (LCs), holographic lithography method is limited. The fabrication requires full coverage of light intensity, 2D chiral distribution an...

Newly developed ferroelectric liquid crystal (FLC) with submicron helix pitch p 0 comprises advantages of both nematic and smectic C* phases in terms of steadiness to the mechanical stress and high contrast ratio more than 7000:1 at the operation frequency range up to 1 kHz with 1V/m applied electric field. Explanation of late news status Shock-f...

A ferroelectric liquid crystal (FLC) cell with continuously alignment structure is realized by a polarization hologram method for fabricating a Pancharatnam-Berry (PB) lens, which is employed as a concave/convex lens. The PB phase can be maintained by the optical axis in-plane switching; meanwhile, its diffraction efficiency can be tuned in a certa...

We report on fast-switching and high-efficient optical beam steering based on a polymerisable liquid crystal polarisation grating (PG) in combination with ferroelectric liquid crystal (FLC) phase shutter. The PG was fabricated in a convenient single-step holographic exposure process using photo-sensitive azo-dye material as alignment layer for liqu...

We disclose a method of fabricating a low-voltage-driven smart glass based on micro-patterned liquid crystal (LC) Fresnel lenses and implement three proof-of-concept prototypes. Distinct from the conventional LC-based smart windows with the scattering state, the prominence of our proposed LC smart glass in blurry state under both normal and oblique...

It is very difficult to display greyscale for an optically driving liquid crystal display (ODLCD) because the driving unit and display unit are separate, and there are no electronics in the display part of ODLCD. In this paper, two greyscale generation methods are proposed to achieve this goal. Six and nine grey levels are separately achieved throu...

Experimentally shown that the shear flow of a ferroelectric smectic C* liquid crystal (FLC) in flat capillary with homeotropic boundary conditions can be described in the framework of the Newtonian fluids theory if the pitch p0 of the FLC helix is much less than the capillary gap. The motion of the contact line during the filling of the capillary w...

We present the design methodology of a light reconfigurable geometric phase optical element with multi-stable diffraction efficiency states, enabled by a photoresponsive self-organized chiral liquid crystal. Experimental demonstration shows the device exhibits a broad diffraction efficiency tunable range that can be smoothly modulated under alterna...

The results of experimental investigation of rheological properties of a nematic liquid crystal (NLC) 5CB (4-cyano-4′-pentylbiphenyl) confined to submicron pores of polymer PET-films in the presence of AC electric field are presented. The decay flow method, elaborated previously for plane channels, was successfully adopted and applied to the LC-PET...

Electro-optical and spectral studies of isotropic photonic crystal fibre (PCF) infiltrated with photo-aligned ferroelectric liquid crystal (FLC) under influence of external electric field are described. Desired alignment of FLC molecules is provided by generation of photo-aligning surface on the inner side of PCF structure. Propagation of light spe...

To date, azo dyes are widely used for liquid crystal photoalignment in flat panel displays. The relation of dichroism of azo dyes with their orientation under intensive light wave field is considered. Values of a parameter, which characterizes orientation order of both molecules and dimers, were obtained as well as energy of their orientation proce...

Process optimisation for increasing the response speed of optical driving liquid crystal cell was investigated in this paper. It is demonstrated that by filling LC in atmosphere condition rewriting time could be decreased to 6 s with good repeatability. Increasing the spin coating speed, the rewriting time could also decrease the azimuthal anchorin...

A liquid crystal Pancharatnam-Berry (PB) axilens is proposed and fabricated via a digital micro-mirrordevice-based photo-patterning system. The polarization-dependent device behaves as an axilens for a lefthanded circularly polarized incident beam, for which an optical ring is focused with a long focal depth in the transverse direction at the outpu...

The local optical anisotropy of 1D semiconductor nanorods (NRs), which results in anisotropic absorption and polarized emission, is important for various applications. Thin films of photoaligned, oriented NRs offer not only polarized emission but also anisotropic absorption at the macroscopic scale. Based on this anisotropic absorption, two kinds o...

In this article, we disclose a 3‐inch 250ppi active matrix field sequential color (FSC) display based on electrically suppressed ferroelectric liquid crystal (ESHFLC). ESHFLC's ultra‐fast response time (~10 μs at 6.67 V/μm) enables the display resolution to be tripled via FSC technique. The photo‐alignment technology provides ESHFLC with optimal an...

Diffractive optical elements based on patterned photoalignment analogous to multi‐domain LCD alignment patterning, dammann grating (DG) and random grating (RG), are demonstrated in this paper. Diffractive optical devices can act as transparent displays or smart windows. Key to the fabrication of our gratings, which are photo‐aligned with azo‐type m...

In this paper, the composite film of nanorods and liquid crystal polymer, which could offer liquid crystal azimuthal anchoring energy, is introduced as an in‐cell orientation layer for liquid crystal displays. The emission patterns from NRs pixels on the fabricated liquid crystal panel are controlled by only 5 Volts.

In this article, we disclose a 3‐inch 250ppi active matrix field sequential color electrically suppressed ferroelectric liquid crystal (ESHFLC) display. ESHFLC's ultra‐fast response time (~10µs at 6.67V/µm) enables the display resolution to be tripled via field sequential color technique. Photo‐alignment technology provides ESHFLC with optimal anch...

We report fabrication of a photoaligned quantum rods (QRs) brightness enhancement films (QREF) for LCDs by using inkjet‐printing. The printed QRs on the pre‐aligned photosensitive alignment layers show high‐quality alignment and so emits polarized light with a degree of polarization ~ 0.75. The optimized inkjet printing allows us to print large are...

The possibility and features of formation of sensitized photoinduced optical anisotropy in amorphous films of poly(vinyl cinnamate) and its derivative poly(vinyl-4-metoxicinnamate) under the action of polarized light (including light that is not absorbed by polymer macromolecules themselves) have been investigated. It is found that the effect of in...

A tunable spatial light modulator, dammann grating, based on patterned photoalignment is demonstrated in this paper. Key to the fabrication of it, which is photo‐aligned with azo‐type material, is the ability of the material to be rewritable, i.e. it usually realigns upon rewriting. By adjusting electrical field, the grating can be switched between...

In this article, we disclose a 3‐inch 250ppi active matrix field sequential color electrically suppressed ferroelectric liquid crystal (ESHFLC) display. ESHFLC's ultra‐fast response time (~10µs at 6.67V/µm) enables the display resolution to be tripled via field sequential color technique. Photo‐alignment technology provides ESHFLC with optimal anch...

Azobenzene materials provide an effective way for liquid crystal (LC) alignment besides traditional rubbing technology. A strong relationship between relative humidity (RH) and the photoalignment quality of hydrophilic azobenzene dye brilliant yellow (BY) has been investigated. Good photoalignment quality can only be ensured at about 40% RH or belo...

It is very difficult to make a liquid crystal display (LCD) that is flexible. However, for an optically re-writable LCD (ORWLCD), only the spacers and the substrates need to be flexible because the driving unit and the display unit are separate and there are no electronics in the display part of ORWLCD. In this paper, three flexible-spacer methods...