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Crystals
Special Issues
Liquid Crystal Optics and Physics: Recent Advances and Prospects
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Liquid Crystal Optics and Physics: Recent Advances and Prospects

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Liquid Crystals".

Deadline for manuscript submissions: closed (20 July 2019) | Viewed by 33727

Special Issue Editors

Prof. Chun-Ta Wang

E-Mail Website
Guest Editor
Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan
Interests: liquid crystal optics, chiral-nematic liquid crystal, blue phase, photo-aligning technique for LC devices, soft-matter physics, silicon photonics
Prof. Dr. Chan-Shan Yang

E-Mail Website
Co-Guest Editor
1. Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei, Taiwan
Interests: terahertz photonics; liquid crystal optics; graphene (and 2D material) optoelectronics; ultrafast photonics; nonlinear optics
Prof. Dr. Qi Guo

E-Mail Website
Co-Guest Editor
School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China
Interests: photo-alignment for ferroelectric liquid crystals; fast-response devices based on ferroelectric liquid crystals; photo-aligned liquid crystals for polarization detection
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Liquid crystals (LC) have been extensively investigated for more than 100 years. They possess orientational/positional orders as a crystalline solid and fluidity as a liquid. Surprisingly, there are a number of physical properties that are unique to LC, including large physical anisotropies and viscoelasticity, and high susceptibility to external stimuli. Therefore, LCs are oftentimes the best optical material for applications ranging from displays to sensors and photonic circuits. LC optics and physics are still growing fields of research, and many scientific and technological breakthroughs have been made over the past few years. Emerging display technologies, such as see-through displays, augmented reality (AR), and virtual reality (VR) display systems, have been developed and created new design/application possibilities. Low power consumption also makes LC promising for energy-saving applications such as smart windows. For photonic applications, diffractive optical elements based on LCs realized by a patterned surface are powerful tools for complex spatial field shaping; photonic-crystalline LCs (e.g., cholesteric and blue phases) are employed for manipulating light spectrally and/or temporally and generating lasers. Besides the technological advances, fundamental physics research on topics such as topological defects and nonlinear optics are also of great interest. LCs are known to possess a wide variety of collective nonlinear optical phenomena, and countless types of topological defects are easily generated and manipulated in LCs. At last, we would like to note that LC optics have been expanded from the traditional UV–Vis–NIR spectrum to mid-IR, THz, and microwave regimes, thanks to their ultra-broadband birefringence.

This Special Issue is aimed at both basic and applied research, concentrating on the optics and physics of Liquid Crystals, as well as their use in various applications. Besides original research articles, we also encourage submission of review papers on recent advances and future prospects of LC technologies and challenges. Topics for the feature issue will include, but are not limited to, the following:

  • Topological defects and nanoparticle self-assembly
  • Optical properties and applications of LCs in mid-IR, THz, and microwave regimes
  • Nonlinear optics (e.g., EFISH and photorefractive effect)
  • Multi-stable operations in LCs and their applications (e.g., smart optical switches, energy-saving windows, and reflective displays)
  • Flat optics: diffractive (geometric-phase) optical elements based on photoalignment (e.g., optic-axis grating, q plate, and lens)
  • Novel display technologies (e.g., transparent, AR, VR, and holographic displays)
  • Bio, chemical, and vibration sensors
  • Photonic-crystalline LCs (e.g., chiral nematic, chiral smectic, and blue phases) and LC-infiltrated photonic crystals

Active integrated photonic devices (e.g., waveguide, fiber, photonic crystal, metamaterials, and plasmonics)

Prof. Chun-Ta Wang
Dr. Qi Guo
Prof. Chan-Shan Yang
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • LC defects
  • LC nonlinear optics
  • LC flat-optics
  • Photonic-crystalline LCs
  • LC displays/sensors/integrated photonic devices

Published Papers (8 papers)

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Editorial

Jump to: Research, Review

2 pages, 140 KiB  
Editorial
Liquid Crystal Optics and Physics: Recent Advances and Prospects
by Chun-Ta Wang, Chan-Shan Yang and Qi Guo
Crystals 2019, 9(12), 670; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9120670 - 12 Dec 2019
Cited by 7 | Viewed by 2030
Abstract
For more than 100 years, liquid crystals (LCs) have been extensively investigated and LC displays now are becoming ubiquitous in our daily life, from TVs, mobile phones to indoor/outdoor signage [...] Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)

Research

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9 pages, 3478 KiB  
Article
Multi-Wavelength Filters of Templated Blue Phase Liquid Crystal
by Shenghao Zha, Hongzhou Zhang, Changli Sun, Yifan Feng and Jiangang Lu
Crystals 2019, 9(9), 451; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9090451 - 30 Aug 2019
Cited by 11 | Viewed by 3059
Abstract
The multi-wavelength filters in the visible light band using the blue phase liquid crystal (BPLC) template was investigated. A multi-layer templated BPLC (T-BPLC) filter without intermediate dielectric layers was fabricated, which may reflect multi-wavelength in one filter. Compared with the cholesteric liquid crystal [...] Read more.
The multi-wavelength filters in the visible light band using the blue phase liquid crystal (BPLC) template was investigated. A multi-layer templated BPLC (T-BPLC) filter without intermediate dielectric layers was fabricated, which may reflect multi-wavelength in one filter. Compared with the cholesteric liquid crystal (CLC) filter, the T-BPLC filter may get a much narrower reflection bandwidth (<15 nm), show better angular stability of incident light, and have a more stable wavelength and bandwidth with a temperature shift. Furthermore, the central wavelength and bandwidth can be easily controlled by the fabrication process and the optimization of the material concentration. When the incident angle varies, the shift of the center wavelength of the T-BPLC filter is much smaller than that of the CLC filter. The multi-wavelength filter shows a potential application in color filters and high-density wavelength division multiplexed networks. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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10 pages, 3559 KiB  
Article
Electrically Tunable-Focusing Liquid Crystal Microlens Array with Simple Electrode
by Li-Lan Tian, Fan Chu, Hu Dou, Lei Li and Qiong-Hua Wang
Crystals 2019, 9(8), 431; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9080431 - 20 Aug 2019
Cited by 8 | Viewed by 3474
Abstract
An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and [...] Read more.
An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and an LC microlens is generated between the two strip electrodes. For each LC microlens, the gap between the top planar electrodes is directly above the center of the microlens. Unlike the conventional LC lens, the individual LC microlens is not coated with ITO electrodes on the central part of its upper and lower substrates, which helps to maintain the LC’s horizontal orientation. In the voltage-off state, the focal length of the microlens array is infinity because of the homogeneous LC alignment. At a given operating voltage, an ideal gradient refractive index distribution is induced over the homogeneous LC layer, which leads to the focusing effect. The simulation result shows that the focal length of the LC microlens could be gradually drawn to 0.381 mm with a change of voltage. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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8 pages, 2342 KiB  
Article
A Tunable NIR Filter with Sphere Phase Liquid Crystal
by Changli Sun and Jiangang Lu
Crystals 2019, 9(7), 349; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9070349 - 08 Jul 2019
Cited by 8 | Viewed by 2986
Abstract
A near-infrared (NIR) filter with sphere phase liquid crystal (SPLC) is proposed, which shows a low operating electric field and large temperature-gradient modulations. The central wavelength of the Bragg reflection can be thermally tuned from 1580 nm to 1324 nm with a temperature-gradient [...] Read more.
A near-infrared (NIR) filter with sphere phase liquid crystal (SPLC) is proposed, which shows a low operating electric field and large temperature-gradient modulations. The central wavelength of the Bragg reflection can be thermally tuned from 1580 nm to 1324 nm with a temperature-gradient of 42.7 nm/K. Meanwhile, the central wavelength can be electrically tuned over 76 nm within a low operating electric field of 0.3 V/μm. Thus, the SPLC filter may achieve a wavelength variation of 256 nm by thermal modulation and 76 nm by electrical modulation. The SPLC filter shows great potential applications in optical communication devices. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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10 pages, 1870 KiB  
Article
A High-Resolution Terahertz Electric Field Sensor Using a Corrugated Liquid Crystal Waveguide
by Lan-Lan Xu, Yi Gong, Ya-Xian Fan and Zhi-Yong Tao
Crystals 2019, 9(6), 302; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9060302 - 12 Jun 2019
Cited by 3 | Viewed by 2858
Abstract
Liquid crystals (LCs) can always reflect variable optical properties in a broad terahertz (THz) band under external electric or magnetic fields. Based on the measurements of these varying properties, we can realize electric and magnetic field sensing with very high sensitivity. Here, we [...] Read more.
Liquid crystals (LCs) can always reflect variable optical properties in a broad terahertz (THz) band under external electric or magnetic fields. Based on the measurements of these varying properties, we can realize electric and magnetic field sensing with very high sensitivity. Here, we theoretically and numerically demonstrate a type of electric field sensor in the THz frequency range based on the defect mode arising in a periodically corrugated waveguide with liquid crystals. The Bragg defect structure consisting of periodically corrugated metallic walls and a defect in the middle can provide a narrow transmitted peak with controllable bandwidth, which can be used for external field sensing when it is filled with LCs. The molecular orientation of nematic LCs (E7) is not only very sensitive to the applied DC electric field but also very crucial to the effective refractive index of E7. Changing the effective index can efficiently shift the frequency of the transmitted peak in the THz spectrum. The simulated results show that the sensitivity can reach as high as 9.164 MHz/(V/m) and the smallest resolution is 0.1115 V/m. The proposed sensor and its significant performance could benefit electric field sensing and extend the applications of THz technology. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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8 pages, 2122 KiB  
Article
A Fast-Response and Helicity-Dependent Lens Enabled by Micro-Patterned Dual-Frequency Liquid Crystals
by Wei Duan, Peng Chen, Shi-Jun Ge, Xiao Liang and Wei Hu
Crystals 2019, 9(2), 111; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9020111 - 20 Feb 2019
Cited by 16 | Viewed by 4427
Abstract
Liquid crystals are excellent candidates for tunable optical elements due to their large birefringence and continuous tunability by external fields. A dual-frequency liquid crystal lens integrated with Pancharatnam–Berry phase was fabricated via a dynamic photo-patterning technique. The proposed lens exhibited distinctive polarization-dependent characteristics [...] Read more.
Liquid crystals are excellent candidates for tunable optical elements due to their large birefringence and continuous tunability by external fields. A dual-frequency liquid crystal lens integrated with Pancharatnam–Berry phase was fabricated via a dynamic photo-patterning technique. The proposed lens exhibited distinctive polarization-dependent characteristics and ultra-high efficiency rates of up to 95%. Via merely alternating the frequency of the applied electric field, the switching time between unfocused and focused states was measured in submilliseconds. This work supplies a new strategy for fast-response, high-efficiency and helicity-dependent lens with merits of easy fabrication and low power consumption. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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9 pages, 3339 KiB  
Article
Parameter Space Design of a Guest-Host Liquid Crystal Device for Transmittance Control
by Seung-Min Nam, Seung-Won Oh, Sang-Hyeok Kim, Jae-Won Huh, Eunjung Lim, Jinhong Kim and Tae-Hoon Yoon
Crystals 2019, 9(2), 63; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9020063 - 26 Jan 2019
Cited by 10 | Viewed by 4085
Abstract
A transmittance-control device requires a high transmittance difference between its transparent and opaque states. In this paper, we propose a systematic approach to find the condition for the maximum transmittance difference in a guest-host liquid crystal (GHLC) cell. To this end, we calculated [...] Read more.
A transmittance-control device requires a high transmittance difference between its transparent and opaque states. In this paper, we propose a systematic approach to find the condition for the maximum transmittance difference in a guest-host liquid crystal (GHLC) cell. To this end, we calculated the transmittance difference as we varied the cell gap and dye concentration. The transmittance of a GHLC cell is dependent on the alignment of dye molecules, cell gap, and dye concentration. We used a constant-transmittance contour map to find the condition for the desired transmittance of LC cells in each state and the transmittance difference of each LC mode. We experimentally confirmed that the design of a GHLC cell with the desired performance could be achieved through the proposed design process. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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Review

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21 pages, 10074 KiB  
Review
Ferroelectric Liquid Crystals: Physics and Applications
by Qi Guo, Kexin Yan, Vladimir Chigrinov, Huijie Zhao and Michael Tribelsky
Crystals 2019, 9(9), 470; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst9090470 - 09 Sep 2019
Cited by 54 | Viewed by 9930
Abstract
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), [...] Read more.
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. Full article
(This article belongs to the Special Issue Liquid Crystal Optics and Physics: Recent Advances and Prospects)
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