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Liquid Crystals in Photonics

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A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Optoelectronics and Optical Materials".

Deadline for manuscript submissions: closed (20 January 2024) | Viewed by 10096

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Special Issue Editors

Dr. Xiayu Feng

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Guest Editor

Liquid Crystal Institute, Kent State University, Kent, OH, USA
Interests: liquid crystal; AR/VR; waveguide; display; shutter; andpolarization grating

Dr. Yannanqi Li

E-Mail Website
Guest Editor

The College of Optics and Photonics, University of Central Florida, Orlando, FL, USA
Interests: novel liquid crystal devices; optical system design; augmented reality and virtual reality displays

Special Issue Information

Dear Colleagues,

Liquid crystals are a state of matter that exhibit both fluid- and solid-like properties. They are unique in that they have both long-range order, meaning that the molecules are aligned in a specific orientation, and short-range disorder, indicating a random arrangement of the molecules within each orientation. This combination of order and disorder leads to distinctive optical properties that make liquid crystals useful for a range of photonic applications.

A well-known application of liquid crystals is in liquid crystal displays (LCDs), where they are used to produce colors and images in electronic devices, such as smartphones, televisions, and computers. In an LCD, an electric current is applied to the liquid crystal molecules, causing them to align and produce a specific color or image. The widespread use of LCDs in modern technology has made liquid crystals a major contributor to the field of liquid crystal photonics. In addition to LCDs, liquid crystals have been used for various other photonic applications. For example, they have been integrated into optical communication systems, where they can be used as tunable filters to control the wavelength of light. They have also been employed as sensors, where changes in the alignment of the liquid crystal molecules can be used to detect various physical and chemical parameters, as well as in laser technology, where they can be used to control the polarization and direction of laser beams.

Overall, liquid crystal photonics is a rapidly growing and evolving area of research, with novel applications and advancements continuously being developed. The unique optical properties of liquid crystals, combined with their versatility and ease of integration into various photonic systems, make them a valuable tool for researchers and engineers in the field of photonics.

Several key topics in the field of liquid crystals in photonics include the following:

Liquid crystal displays and their technological advancements;
Liquid crystal-based optical communication systems;
Liquid crystal-related AR/VR technologies;
Liquid crystal sensors and their applications in different fields;
Liquid crystal laser technology and its potential applications;
Properties of liquid crystals and their impact on photonic applications;
Theoretical and computational studies of liquid crystals in photonics.

Dr. Xiayu Feng
Dr. Yannanqi Li
Guest Editor

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Keywords

liquid crystals
photonics
AR/VR
LCD
optical communication
sensors
laser technology
electronic devices
computational optics

Published Papers (11 papers)

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Research

8 pages, 1902 KiB

Open AccessArticle

Modal Phase Modulators Based on Liquid Crystals with 3D-Printed Polymer Microstructures: Increasing Size and Complexity

by Alec Xu, Camron Nourshargh, Patrick S. Salter, Steve J. Elston, Stephen M. Morris and Martin J. Booth

Photonics 2024, 11(3), 266; https://doi.org/10.3390/photonics11030266 - 15 Mar 2024

Viewed by 751

Abstract

We present extended capabilities in simple liquid crystal-based devices that are applicable to adaptive optics and other related fields requiring wavefront manipulation. The laser-written devices can provide complex phase profiles, but are extremely simple to operate, requiring only a single electrode pair tuned between 0 and 10 V RMS. Furthermore, the devices operate in the transmissive mode for easy integration into the optical path. We present here as examples three such devices: the first device reproduces the defocus Zernike polynomial; the second device reproduces a seventh-order Zernike polynomial, tertiary coma; and the last example is of a primary spherical aberration. All devices offer wavelength-scale wavefront manipulation up to more than

2 π

radians peak-to-peak phase at a wavelength of 660 nm. The coma correction device is significantly more complex, reproducing a mode two orders higher than previous demonstrations, while the spherical device is nearly a full order of magnitude larger, measuring 2 mm in diameter. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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9 pages, 4955 KiB

Open AccessCommunication

Photo-Aligned Ferroelectric Liquid Crystal Fork Grating-Mediated Fast Switchable Spiral Phase Contrast Imaging

by Qi Guo, Zidi Zhong, Huijie Zhao, Shijie Wang and Kexin Yan

Photonics 2024, 11(1), 85; https://doi.org/10.3390/photonics11010085 - 17 Jan 2024

Viewed by 726

Abstract

Extensive research has been devoted to spiral phase contrast imaging because of its notable capacity to enhance the edges of both phase and amplitude objects. We demonstrate a setup using ferroelectric liquid crystal (FLC) fork grating (FG) to enable switchable spiral phase contrast imaging within sub-milli-second responses. This system enables the electrical toggling between images featuring edge enhancement and those without it. The specially designed FLC FG generates a vortex beam while in a diffractive state and transmits a Gaussian beam when in a transmissive state. Using a two-step photo-alignment method, the produced FLC FG exhibits exceptional efficiency at approximately 35% and impressively rapid switching at around 307 μs. By introducing this method, we expand the potential applications of spiral phase contrast imaging, particularly in fields such as bio-sensing and photonics. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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13 pages, 14665 KiB

Open AccessArticle

Coarse Integral Volumetric Imaging Display with Time and Polarization Multiplexing

by Garimagai Borjigin, Yuqiang Ding, John Semmen, Hosna Tajvidi Safa, Hideki Kakeya and Shin-Tson Wu

Photonics 2024, 11(1), 7; https://doi.org/10.3390/photonics11010007 - 21 Dec 2023

Viewed by 921

Abstract

This paper introduces an innovative approach to integral volumetric imaging employing time and polarization multiplexing techniques to present volumetric three-dimensional images. Traditional integral volumetric imaging systems with a coarse lens array often face moiré pattern issues stemming from layered panel structures. In response, [...] Read more.

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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8 pages, 3419 KiB

Open AccessArticle

The Birefringence and Extinction Coefficient of Ferroelectric Liquid Crystals in the Terahertz Range

by Ying Ma, Yuhang Shan, Yongning Cheng, Ruisheng Yang, Hoi-Sing Kwok and Jianlin Zhao

Photonics 2023, 10(12), 1368; https://doi.org/10.3390/photonics10121368 - 13 Dec 2023

Viewed by 1025

Abstract

In this paper, the refractive index and extinction coefficient of ferroelectric liquid crystals have been examined by the terahertz time-domain spectroscopy system. Two modes of ferroelectric liquid crystal materials, deformed helix ferroelectric liquid crystal (DHFLC), and electric suppressed helix ferroelectric liquid crystal (ESHFLC) are tested as experimental samples. Nematic liquid crystal (NLC) was also investigated for comparison. The birefringence of DHFLC 587 slowly increases with the growth of frequency, and it averages at 0.115. Its extinction coefficients gradually incline to their stable states at 0.06 for o-wave and 0.04 for e-wave. The birefringence of ESHFLC FD4004N remains between around 0.165 and 0.175, and both of its e-wave and o-wave extinction coefficients are under 0.1, ranging from 0.05 to 0.09. These results of FLC will facilitate the examination and improve the response performance of THz devices using fast liquid crystal materials. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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11 pages, 932 KiB

Open AccessArticle

Nonreciprocal Propagation of Nematicons

by Enrique Calisto and Gaetano Assanto

Photonics 2023, 10(10), 1144; https://doi.org/10.3390/photonics10101144 - 12 Oct 2023

Cited by 1 | Viewed by 759

Abstract

We model two-port nonlinear optical isolators based on solitary waveguides in planar cells with non-homogeneously oriented liquid crystals in the nematic phase. In a planar layout with molecular anchoring linearly changing along the sample length or across its width, we conduct numerical experiments on the excitation and propagation of reorientational solitons—“nematicons”—launched in opposite directions from the two ends of the cell. Specifically, in the Kerr-like diffractionless regime corresponding to graded-index waveguides for copolarized weak signals, we investigate the non-overlapping trajectories of forward and backward propagating wavepackets. The resulting non-specular transmission entails optical isolation and diode-like behavior as light propagating backwards does not reach the forward input. The response dependencies on input power, range of angular modulation, and one-photon losses are analyzed with reference to parameters of realistic soft matter. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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13 pages, 4084 KiB

Open AccessArticle

Two-Step Performance Optimization of CsPbBr₃ Perovskite Nanocrystals for Wide Color Gamut Displays

by Junhu Cai, Xiaogang Chen, Wenyan Zhang, Longwen Yang, Zexi Lin, Wenxiao Zhao, Yun Ye, Sheng Xu, Tailiang Guo and Enguo Chen

Photonics 2023, 10(10), 1113; https://doi.org/10.3390/photonics10101113 - 02 Oct 2023

Cited by 3 | Viewed by 1013

Abstract

Owing to their composition-tunable and narrow emissions and high photoluminescence quantum yield (PLQY), inorganic halide perovskite quantum dots (IPQDs) are a promising option for wide color gamut displays. However, their practical applications have been limited by their lattice structure instability and surface defect states. Herein, CsPbBr₃:KBF₄@SiO₂ with improved stability and optical properties is successfully synthesized with a two-step optimization of fluorine (F) anion doping and SiO₂ in situ coating. Compared with bromide (Br), higher electronegativity and a smaller radius of F lead to stronger binding energy with Pb²⁺. Also, F anions can occupy surface Br vacancies. Then, benefiting from the acidic environment provided by BF₄⁻ hydrolysis, tetraethyl orthosilicate (TEOS) can be more easily hydrolyzed on the CsPbBr₃:KBF₄ surface to generate SiO₂ coating, thus further passivating lattice defects and improving environmental stability. Importantly, the PLQY of CsPbBr₃:KBF₄@SiO₂ achieves 85%, and the stability has been greatly improved compared with pure CsPbBr₃. Finally, CsPbBr₃:KBF₄@SiO₂/PDMS, CsPbI₃/PDMS, and CsPbCl₃/PDMS composites with narrow emissions are applied to replace traditional phosphors as color converters for direct-view light-emitting diode (LED) displays or liquid crystal display (LCD) backlights. The color gamut reaches 118.22% under the NTSC standard. Concerning the display field, it suggests likely applications in the future. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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16 pages, 2322 KiB

Open AccessArticle

Waveguide Properties of Homogeneously Aligned Liquid Crystal Layers between ITO Electrodes and Thin Alignment Films

by Serguei P. Palto and Artur R. Geivandov

Photonics 2023, 10(10), 1089; https://doi.org/10.3390/photonics10101089 - 28 Sep 2023

Viewed by 781

Abstract

Numerical studies of the waveguide properties of liquid crystal layers bounded by substrates with indium tin oxide (ITO) electrodes using the finite difference time-domain (FDTD) method are carried out. On the basis of the experimental transmittance spectra of ITO-coated glass substrates in the visible and near-infrared ranges, a Lorentz model describing the dielectric properties of the ITO electrodes is created. Then, by numerical modeling, optical systems including a homogeneously aligned LC layer between the thin alignment films and the ITO electrodes on the quartz substrates are studied. It is shown that, in the case of the use of traditional alignment films or their absence, the ITO electrodes lead to significant resonant losses in the waveguide mode for both TE- and TM-polarized light. The losses mechanism based on a phase-synchronized mode coupling occurring in relatively narrow spectral ranges is discussed. We also propose a method to control and exclude the losses using thin alignment films with a proper thickness and low refractive index. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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13 pages, 7612 KiB

Open AccessArticle

Controlling Plasmon Resonance of Gold and Silver Nanoparticle Arrays with Help of Liquid Crystal

by Ivan Yakovkin and Victor Reshetnyak

Photonics 2023, 10(10), 1088; https://doi.org/10.3390/photonics10101088 - 28 Sep 2023

Viewed by 932

Abstract

The tunability of plasmonic resonances in gold and silver nanosphere arrays on a glass substrate, embedded in a liquid crystal matrix, was explored. The calculations involving the finite element method revealed that the optical properties of these arrays can be modulated by reorienting the liquid crystal. When the liquid crystal director was reoriented between planar and homeotropic configurations in the plane containing the incident wave polarization vector, the plasmonic resonance wavelength shifted within an approximately 100 nm range. A reduced shift of about 40 nm was observed when the reorientation occurred in the plane perpendicular to the polarization. Both metal nanosphere arrays showed notable near-field amplification. Gold achieved up to 18 times the amplification of the incident wave electric field, while silver reached 16 times but showed a remarkable 40 times amplification at the inter-band transition resonance wavelength. This research underscores the potential of using liquid crystal reorientation for controlling the plasmonic lattice resonance in metal nanosphere arrays, opening up new possibilities for adaptable plasmonic devices. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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11 pages, 2130 KiB

Open AccessArticle

Millisecond-Response Nematic Liquid Crystal for Augmented Reality Displays

by Jiaxing Tang, Ran Chen, Zhongwei An, Xinbing Chen and Pei Chen

Photonics 2023, 10(9), 1062; https://doi.org/10.3390/photonics10091062 - 20 Sep 2023

Viewed by 791

Abstract

Developing fast-response liquid crystals (LCs) is an essential way to achieve low cost, high resolution, and good visual experience for augmented reality (AR) displays. In this paper, we optimized one new nematic LC mixture SNUP01 to meet the requirements of fast-response phase-only liquid crystal on silicon (LCoS) devices in AR displays. The photoelectric performance of this new LC mixture and three commercial LC mixtures were further comparatively evaluated, and the 2π phase-change response speed of this new LC mixture was extrapolated. The research results indicate that SNUP01 possesses high birefringence, moderate dielectric anisotropy, low viscoelastic coefficient, low activation energy, and high figure of merit values. When using this LC mixture at 25 °C @ λ = 633 nm, a 2π phase change can be achieved at 5 V with a total response time of up to millisecond response. Widespread applications of this LC mixture for AR displays are foreseeable. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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12 pages, 2082 KiB

Open AccessArticle

Broadband Vortex Beam Modulating System Based on Electrically Controlled Liquid Crystal Devices

by Xinyi Zhou, Zongjie Zhu, Xiangsheng Xie, Lishuang Yao, Fan Fan and Yaqin Zhou

Photonics 2023, 10(9), 1012; https://doi.org/10.3390/photonics10091012 - 04 Sep 2023

Cited by 2 | Viewed by 980

Abstract

Vortex beams with helical phase wavefronts have recently emerged as a research hotspot because of their widespread applications such as ultra-high dimensional information encoding, quantum entanglement, and data transmission due to their unique properties. Research, as of yet, on the easy preparation of vector vortex beams is hindered by technical bottlenecks such as large mechanical modulation errors and limited bandwidths of meta-structured devices in spite of the massive experimental and theoretical breakthroughs in the generation of vortex beams that have been made. To make up for the deficiency in this area, we propose here a broadband vortex beam modulating system based on electrically controlled liquid crystal (LC) devices. An electrically controlled LC q-plate and an LC broadband polarization grating (PG) are integrated in the system as the crux devices. The system enables pure vortex-phase modulation within a wide spectral range in the visible spectrum and electrical control on the output beam intensity of the vortex and Gaussian components. Experiments at different voltages of 533 nm and 632.8 nm were conducted for validation. This system overcomes the complexity and stringent optical path requirements of traditional methods for generating vortex beams, offering an efficient, convenient, and rapidly tunable approach for generating vortex beams that is easily and highly integrable. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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11 pages, 2072 KiB

Open AccessArticle

Anomalous Spectral Shift of o-Modes in Multilayer Photonic Structure Induced by Homeotropic–Homeoplanar Transition in Chiral–Nematic Defect Layer

by Vladimir A. Gunyakov, Vitaly S. Sutormin, Ivan V. Timofeev, Vasily F. Shabanov and Victor Ya. Zyryanov

Photonics 2023, 10(9), 959; https://doi.org/10.3390/photonics10090959 - 22 Aug 2023

Viewed by 630

Abstract

A chiral nematic is embedded between multilayer mirrors to obtain voltage-inducible polarized resonance spectra. Initially, the nematic director is uniformly oriented perpendicular to the mirrors’ surfaces because the chiral nematic helix is completely untwisted due to the homeotropic boundary conditions specified by the adsorbed cations. Then, a voltage is applied to remove the layer of surface-active cations from the input mirror. The obtained twisted homeoplanar configuration has a helix pitch exceeding the layer’s thickness. The twisting leads to the anomalous blue shift of the o-modes in the transmittance spectrum of the photonic structure. This blue shift can be effectively compensated by repulsion of spectral peaks as a result of mode coupling in the vicinity of the virtual avoided crossing point. The experimental results obtained are confirmed numerically using the 4 × 4 transfer matrix method and explained with the contribution of a geometric phase. Full article

(This article belongs to the Special Issue Liquid Crystals in Photonics)

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