V.G. Chigrinov

V.G. Chigrinov
The Hong Kong University of Science and Technology | UST · Department of Electronic and Computer Engineering

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648
Publications
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10,275
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Publications

Publications (648)
Article
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...
Article
Full-text available
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...
Article
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...
Conference Paper
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...
Article
Full-text available
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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
Article
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...
Article
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.
Article
Full-text available
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...
Article
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...
Article
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...
Article
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,...
Article
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...
Article
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.
Article
Full-text available
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...
Article
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...
Article
Full-text available
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...
Article
Full-text available
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...
Article
Full-text available
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
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...
Conference Paper
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Full-text available
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...
Preprint
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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.
Article
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...
Article
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...
Article
Full-text available
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...
Article
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...
Article
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...
Article
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...
Article
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...
Article
Full-text available
In this paper we consider new possibilities to control the THz irradiation via usage of the previously studied [1] electro-kinetic phenomena in the porous polymer (PET) film filled with a nematic liquid crystal (NLC). It is shown that a sample of the porous film may play the role of electro-hydrodynamic (EHD) pump, which induces a shear Poiseuille...
Article
Full-text available
A two-dimensional (2D) pure polarization pattern via four-beam polarization interferometry of circularly polarized beams is demonstrated both theoretically and experimentally. The polarization orientation of the interference pattern is recorded by an azobenzene photoalignment layer and transferred to liquid crystal (LC), enabling the fabrication of...
Article
Full-text available
Photobiomodulation or low-level light therapy (LLLT) has extensive applications based on light-induced effects in biological systems. Photobiomodulation remains controversial because of a poorly understood biochemical mechanism limited by the well-known biphasic dose response or Arndt-Schulz curve. The Arndt-Schulz curve states that an optimal dose...
Article
Terahertz (THz) phase shifters are an essential component needed to realize many potential applications. Liquid crystals (LC) are commonly used at optical frequencies, yet to achieve an equivalent phase shift at THz frequencies the LC layer needs to be orders of magnitude thicker. Consequently, the time for the LC to relax back to its initial state...
Article
Full-text available
We study experimentally electro-optical modulation in a planar aligned deformed-helix ferroelectric liquid crystal (DHFLC) with subwavelength helix pitch that is less than 100 nm, while thickness of the liquid crystal layer is around 50 μm. The electrically tunable phase shift of light from 0 to 2p and the ellipticity of the transmitted light were...
Article
Full-text available
We reveal a 2D–3D switchable lens unit that is based on a polarization-sensitive microlens array and a polarization selector unit made of an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) cell. The ESHFLCs offer a high contrast ratio (~10k∶1) between the crossed polarizers at a low applied electric field (∼1.7 V∕μm) with a smal...
Article
Full-text available
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports on this subject have been i...
Article
For a liquid crystal display device, like optically rewritable (ORW) e-paper, the response time plays a crucial role. In this article, a new method is proposed to increase the rewriting speed of ORW e-paper. Effective rotational viscosity is very important for the dynamic result, the rewriting time can be increased by four times by applying electri...
Article
Semiconductor nanorods (NR) emit polarized light, which is expected to bring manifold benefits, in terms of brightness and color enhancement, for modern liquid-crystal displays (LCD). In this regard, photoaligned nanorod enhancement films (NREF) for color and polarization conversion for LCD backlights are introduced here. The photoinduced anchoring...