Electrically tunable holographic polymer templated blue phase liquid crystal grating

He, Zhenghong; Chen, Chao-Ping; Zhu, Jiliang; Yuan, Ye; Li, Yan; Li, Xiao; Li, Hongjing; Lu, Jiangang; Su, Yikai

doi:10.1088/1674-1056/24/6/064203

Cited by 17 publications

(12 citation statements)

References 46 publications

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“…The diffraction efficiencies in the experiment are defined as the ratio of the diffracted intensity to the incident light intensity. With the increase of the applied voltage, the diffraction efficiency increases and reaches the peak of 21.1% when the applied voltage is 40 V. The peak electric field (4 V/ȝm) is much lower compared PDLC and PSBPLC gratings (~10 V/ȝm) [8,17]. The response times for the PNLC grating were also measured in the experiment.…”

Section: Resultsmentioning

confidence: 97%

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P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

Huang

Yuan

et al. 2016

SID Symposium Digest of Technical Papers

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In this paper, we report a polymer network liquid crystal grating fabricated using interfered visible light. Exposed to the periodic light pattern, polymer concentration gradient is achieved as the precursor is cured. The grating is simple to fabricate and has low voltage, sub-millisecond response and high spatial resolution. Author KeywordsPolymer network liquid crystal; grating; fast response BackgroundElectrically tunable liquid crystal (LC) diffraction gratings have advantages of light weight, low cost and low power consumption [1][2][3][4][5]. Their electro-optical properties can be conveniently tuned by external voltages. However, the response time of conventional nematic LC is relatively slow (~10-100 ms) [6]. To shorten the response time of the gratings, polymer-dispersed liquid crystal (PDLC) [7], polymer-stabilized blue phase liquid crystal (PSBPLC) [8] and polymer network liquid crystal (PNLC) have been adopted in the gratings [9][10][11][12]. Both PDLC and PSBPLC can achieve submillisecond switching time, however, due to the optically quasi-isotropic off-states, their phase change is limited to ~1/3 of that of regular nematic LC gratings. Moreover, relatively high operating electric fields are required (~10V/ȝm) [8,17].On the other hand, PNLC gratings owing to the alignment effect and polymer network anchoring, can achieve both large phase change and relatively low operating voltage. There are several methods to form refractive index gradient in PNLC materials such as exposing a homogeneous LC/monomer mixture with an inhomogeneous UV light using a photomask [13][14] and controlling the tilt angle of a homogeneous cell containing LC/monomer mixture [15][16]. Most methods use photomasks to control the light intensity which makes the grating period relatively large (~100ȝm) and the fabrication processes complicated.In this work, we use interfered visible laser light to fabricate PNLC gratings. Using a visible-curable precursor, polymerization process and polymer-concentration-gradient are achieved simultaneously. The grating exhibits sub-millisecond response time and relatively low voltage. Moreover, via visible laser holography, high spatial resolution could be conveniently achieved at low cost. Grating operation principleThe fabrication process and operation principle of the proposed PNLC grating are depicted in figure 1. As shown in Fig. 1(a), a homogeneous cell is filled with LC/monomer mixture. The inner surfaces of the top and bottom glass substrates are over-coated with thin transparent indium-tin-oxide (ITO) electrodes, followed by polyimide alignment layers. Then the cell is exposed to the alternative dark and bright interference light pattern. Because the polymerization preferentially occurs in the bright regions, more monomers are consumed, causing a monomer concentration gradient between bright and dark regions. Thus, the monomers will diffuse from dark regions to adjacent bright regions as shown in Fig. 1(b) [16]. Therefore, a denser polymer network is formed in the bright regions wh...

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Section: Resultsmentioning

confidence: 97%

“…Both PDLC and PSBPLC can achieve submillisecond switching time, however, due to the optically quasi-isotropic off-states, their phase change is limited to ~1/3 of that of regular nematic LC gratings. Moreover, relatively high operating electric fields are required (~10V/ȝm) [8,17].…”

Section: Introductionmentioning

confidence: 99%

P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

Huang

Yuan

et al. 2016

SID Symposium Digest of Technical Papers

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“…DOE: DOE is an array of slanted gratings, which can be fabricated with electron-beam [19], holographic [20], or nanoimprint lithography [21]. The number of slanted gratings shall match with the resolution of scanning laser projector.…”

Section: Design Rulesmentioning

confidence: 99%

P‐92: A Lensless Retinal Scanning Display for Augmented Reality

Chen

et al. 2019

Symp Digest of Tech Papers

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“…The typical PDLC device can switch between a transparent state and a light scattering state by the electric field. It also has been used in a variety of optical devices such as switchable windows [6], shutters [7], gratings [8], etc. Therefore, PDLCs can be operated without a polarizer, thus reducing the loss of light.…”

Section: Introductionmentioning

confidence: 99%

Electro-Optical Effects of a Color Polymer-Dispersed Liquid Crystal Device by Micro-Encapsulation with a Pigment-Doped Shell

2019

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Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix. A conventional PDLC device is fabricated by phase separation. However, this method leads to non-uniform electro-optical characteristics of the device due to the non-uniform size distribution of the liquid crystal droplets. Moreover, the PDLC device is switched between the transparent state and the scattering state so that a full color scheme is intrinsically impossible without a color filter. In this paper, a fabrication method for a color PDLC device with uniform size and shape for liquid crystal droplets is proposed. Droplets of a fairly uniform size in large quantities can be obtained by means of membrane emulsification. Microcapsules are fabricated by complex coacervation with gelatin and gum arabic. By adding red, green, and blue pigments, color microcapsules are obtained. The electro-optical effects of the fabricated color PDLC devices are also demonstrated. The driving voltage of the device is 90 V, and the switching time is 8.3 ms. In the turn-on state, the measured hazes of red, green, and blue PDLC devices are 16.89%, 15.82%, and 18.55%, respectively, while in the turn-off state, the measured hazes of those devices are 65.21%, 67.32%, and 70.76%, respectively.Crystals 2019, 9, 364 2 of 11 substantially increase. In the guest-host mode, the color shift is caused by the anisotropic properties of the dichroic dye. Moreover, this type of device is short-lived, because the dichroic dye is vulnerable to ultraviolet light.To address both the non-uniform size distribution and the full color display, we propose a color PDLC device, which is characterized by a colored core-shell structure. The fabrication process of color PDLCs with a core-shell structure of uniform size is investigated. The electro-optical properties are also demonstrated in terms of the voltage-transmittance curve, response time, and spectroscopic properties. Materials and Methods Formation of Liquid Crystal Droplets by Membrane EmulsificationMembrane emulsification is an emulsification technique, for example, the Shirasu-porous-glass membrane emulsification method to make monodispersed emulsions developed by Nakashima et al. [13]. It is suitable for the fabrication of all types of droplets, including oil in water emulsion and water in oil emulsion. Also, membrane emulsification can form small-sized and uniform droplets. The schematic diagram of the droplet-forming process is depicted in Figure 1. The dispersed phase escapes through the porous membrane filter into the moving continuous phase. At the surface of membrane filter, the dispersed droplets, which pass though the pore of the filter, will be detached by the shear stress in the continuous phase. In this way, droplet size can be effectively controlled by the shear stress.

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Electrically tunable holographic polymer templated blue phase liquid crystal grating

Abstract: He Zheng-Hong(何正红) a)b) , Chen Chao-Ping(陈超平) a) † , Zhu Ji-Liang(朱吉亮) a) , Yuan Ya-Chao(袁亚超) a) , Li Yan(李燕) a) ‡ , Hu Wei(胡伟) a) , Li Xiao(李潇) a) , Li Hong-Jing(李洪婧) a) , Lu Jian-Gang(陆建刚) a) , and Su Yi-Kai(苏翼凯) a)

Cited by 17 publications

References 46 publications

P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

P‐92: A Lensless Retinal Scanning Display for Augmented Reality

Electro-Optical Effects of a Color Polymer-Dispersed Liquid Crystal Device by Micro-Encapsulation with a Pigment-Doped Shell

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Electrically tunable holographic polymer templated blue phase liquid crystal grating

Abstract: He Zheng-Hong(何正红) a)b) , Chen Chao-Ping(陈超平) a) † , Zhu Ji-Liang(朱吉亮) a) , Yuan Ya-Chao(袁亚超) a) , Li Yan(李 燕) a) ‡ , Hu Wei(胡 伟) a) , Li Xiao(李 潇) a) , Li Hong-Jing(李洪婧) a) , Lu Jian-Gang(陆建刚) a) , and Su Yi-Kai(苏翼凯) a)

Cited by 17 publications

References 46 publications

P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

P-139: Polymer Network Liquid Crystal Grating Cured with Interfered Visible Light

P‐92: A Lensless Retinal Scanning Display for Augmented Reality

Electro-Optical Effects of a Color Polymer-Dispersed Liquid Crystal Device by Micro-Encapsulation with a Pigment-Doped Shell

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Product

Resources

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Abstract: He Zheng-Hong(何正红) a)b) , Chen Chao-Ping(陈超平) a) † , Zhu Ji-Liang(朱吉亮) a) , Yuan Ya-Chao(袁亚超) a) , Li Yan(李燕) a) ‡ , Hu Wei(胡伟) a) , Li Xiao(李潇) a) , Li Hong-Jing(李洪婧) a) , Lu Jian-Gang(陆建刚) a) , and Su Yi-Kai(苏翼凯) a)