Optical Characteristics of Double Layered Chiral Liquid Crystal

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Analytical Design of Double Layered Chiral Liquid Crystal Color Filter

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Electrically Stretchable Color Change Using Chiral Photonic Gels

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Analytical Study of Bi-Layered Chiral Liquid Crystal Photonic Band Filter

Owing to their peculiar helical structure, Chiral Liquid Crystals (CLCs) are well known for the selective spectral photonic band. This unique photonic band property is resulted from the optical rotation effect of electromagnetic wave propagation depending on the material birefringence (Δn) and rotational repeating pitch (p) following the elegant equation Δλ=Δn·p. Hitherto, a number of researchers have investigated the photonic bandgaps (PBGs) control of this fascinating chiral liquid crystal materials for various applications [1,2]. In particular, over visible wavelength range, the concept of the selective color filter exploiting the optical characteristics of CLCs can be suggested beyond the Bayer color filter which is based on chemical dye absorption. Especially, from the well design of chiral liquid crystal parameter, well controllable tuning of the wavelength position is possible in CLC band filter. In addition to the single CLC structure, bi-layered CLCs can be approached for further elaborate photonic filters [3].Herein, we studied a mathematical analysis of the reflection and transmission spectra of the bilayer CLC photonic color filter modeling. Through this analytical modeling, it was possible to achieve an in-depth understanding of the optical properties of the bilayer CLC color filter. In addition, this study will contribute to exploring a variety of further promising CLC applications including selective band filters and other various photonics sensing applications.1

Analytical design of optical color filter using bi-layered chiral liquid crystal

We introduce an optically controllable color filter model using bi-layered CLC structure. From mathematical parameter sweep analysis using 4×4 matrix method, wavelength controls of red, green, and blue optical color filters and tailored tuning of optical purity in terms of FWHM from 105 nm down to 21 nm at green colored position were confirmed. In addition, an improved color gamut of optical color filters up to 162% of sRGB space in CIE 1931 was first reported. Facile design of custom color filter with controlled wavelength and FWHM, along with enhanced color gamut, can be used for various optical applications.11Ysciescopu

Optical Characteristics of Stretchable Chiral Photonic Film based on Chiral Liquid Crystals via in situ Photopolymerization

Chiral liquid crystals (CLCs) spontaneously form a supramolecular helical structure due to the helicoidal molecular rotations. This helical structure of CLC provides a periodic variation of dielectric tensor and results in electromagnetic light propagation forbidden band so-called photonic band gaps (PBGs) [1]. Similar to other LC phase materials, CLC shows stimulus responsive behaviours against various external stress including light, temperature, electric field, and mechanical strain. Thanks to the self-organizing feature of photonic band structures as well as, the band tunability by various external stimuli, CLCs have attracted considerable interest in diverse applications, such as sensors [2], laser devices [3], and reflective displays [4]. Especially, the PBG tuning by mechanical deformation is of interest for sensing or micro-actuating applications with great potential. Among several fabrication methods for mechanochromic CLC gels, including anisotropic deswelling or inducing biaxial stress method, in situ photopolymerization grants us highly aligned samples with qualitative optical performance and a simple fabrication process. In this study, we demonstrate the fabrication procedure and optical characteristics by a mechanical strain of free-standing CLC film via in situ photopolymerization (Fig.1).1

Mechanochromic Response Behaviors of Stretchable Chiral Photonic Gels

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Optical Characteristics of Deformable Photonic Gels based on Chiral Nematic Liquid Crystal Polymers

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Photonic Band Tuning of Chiral Liquid Crystalline Elastomer using Electrically Stretchable Soft Actuator

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Broadband wavelength tuning of electrically stretchable chiral photonic gel

Chiral photonic-band structure provides technical benefits in the form of a self-assembled helical structure and further functional wavelength tunability that exploits helical deformation according to pitch changes. The stopband wavelength control of the chiral photonic-band structure can be obtained by individual electrical methods or mechanical stretching deformation approaches. However, research on combined electric control of stretchable chiral photonic-band wavelength control while ensuring optical stability during the tuning process has remained limited till now. In this study, using the hybrid structure of elastomeric mesogenic chiral photonic gels (CPGs) with an electrically controlled dielectric soft actuator, we report the first observation of electrically stretchable CPGs and their electro-mechano-optical behaviors. The reliable wavelength tuning of a CPG to a broadband wavelength of ∼171 nm changed with high optical stability and repeated wavelength transitions of up to 100 times. Accordingly, for the first time, electrical wavelength tuning method of stretchable chiral liquid crystal photonicband structure was investigated.11Ysciescopu