Direction-tunable cholesteric phase gratings

Yao, I-An; Liaw, Chien-Huang; Chen, Shu‐Hsia; Wu, Jin−Jei

doi:10.1063/1.1767967

Cited by 15 publications

(8 citation statements)

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“…The stripe direction of CLC gratings has also attracted the interest of researchers. [6][7][8] Yao et al proposed a direction-tunable CLC grating with homeotropic alignment and pattern electrode. 7 Nose et al also demonstrated voltage-dependent rotational diffraction gratings in hybrid aligned LC cells.…”

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confidence: 99%

“…[6][7][8] Yao et al proposed a direction-tunable CLC grating with homeotropic alignment and pattern electrode. 7 Nose et al also demonstrated voltage-dependent rotational diffraction gratings in hybrid aligned LC cells. 8 However, because stripe direction was dependent on voltage, maintaining their direction was problematic when tuning the period by electric field.…”

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confidence: 99%

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Direction switching and beam steering of cholesteric liquid crystal gratings

Jau

Lin

Chen

et al. 2012

Applied Physics Letters

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Highly efficient twisted nematic liquid crystal polarization gratings achieved by microrubbing Appl. Phys. Lett. 101, 041107 (2012) A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell J. Appl. Phys. 112, 024505 (2012) Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystals This work proposes two mechanisms for switching the direction of stripes in cholesteric liquid crystal (CLC) gratings. The stripe direction depends on the ratio of cell gap to the natural pitch length (d/P 0 ) of a CLC sample. Electrical switching is based on the different pitches at the planar and the transient planar states. Optical switching, however, changes pitch by using the photo-isomerization effect of the azobenzene doped in a CLC sample. Using the two mechanisms, we can switch the stripe directions in two orthogonal directions. Furthermore, the beam-steering capability of CLC gratings also remains effective after switching directions. V C 2012 American Institute of Physics. [http://dx.

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confidence: 99%

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confidence: 99%

Direction switching and beam steering of cholesteric liquid crystal gratings

Jau

Lin

Chen

et al. 2012

Applied Physics Letters

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“…Here, they could achieve a large beam steering angle by continuous tuning of the pitch. Yao et al have demonstrated direction‐tunable, i.e., rotatable CLC gratings using patterned electrodes . In these gratings, the helical axis of the CLC rotates in the plane of the substrate and the rotation is controllable by the applied field.…”

Section: Control Of the Helical Axis Of Clcs By Different Stimulimentioning

confidence: 99%

Stimuli‐Driven Control of the Helical Axis of Self‐Organized Soft Helical Superstructures

2018

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Supramolecular and macromolecular functional helical superstructures are ubiquitous in nature and display an impressive catalog of intriguing and elegant properties and performances. In materials science, self-organized soft helical superstructures, i.e., cholesteric liquid crystals (CLCs), serve as model systems toward the understanding of morphology- and orientation-dependent properties of supramolecular dynamic helical architectures and their potential for technological applications. Moreover, most of the fascinating device applications of CLCs are primarily determined by different orientations of the helical axis. Here, the control of the helical axis orientation of CLCs and its dynamic switching in two and three dimensions using different external stimuli are summarized. Electric-field-, magnetic-field-, and light-irradiation-driven orientation control and reorientation of the helical axis of CLCs are described and highlighted. Different techniques and strategies developed to achieve a uniform lying helix structure are explored. Helical axis control in recently developed heliconical cholesteric systems is examined. The control of the helical axis orientation in spherical geometries such as microdroplets and microshells fabricated from these enticing photonic fluids is also explored. Future challenges and opportunities in this exciting area involving anisotropic chiral liquids are then discussed.

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“…As the results of orientation disorder of cholesteric fringes such as lying‐helix structures cannot be effectively used as a diffraction optical element. Nevertheless, there are methods to obtain an aligned fingerprint structures, which were used to create tunable DGs . In the paper, the authors used nematic 5CB doped with a mixture of nonphotochromic and photochromic chiral dopants 4 and 5, respectively (Figure b).…”

Section: Periodic Structures Spontaneously Forming In Clc Layersmentioning

confidence: 99%

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Ryabchun

Bobrovsky

2018

Advanced Optical Materials

196

106

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refractive, diffraction and optical fiber components. In particular, diffraction grating (DG) is one of the key elements for the design and creation of modern optoelectronic devices. One of the most prominent materials for the creation of DGs is liquid crystals. The main feature of these systems is that liquid crystals combine properties such as optical anisotropy inherent for crystals and molecular mobility. High sensitivity to an external field, in particular to an electric field, makes liquid crystals very useful for the creation of DGs with tunable properties. The combination of these properties enables easy control of optical characteristics of such systems and opens wide perspectives for the design of new materials for diffractive optics.Among the different types of liquid crystalline (LC) phases, cholesteric liquid crystal (CLC) phase possesses intrinsic periodicity in the form of the helical supramolecular structure (Figure 1). With the realization of definite alignment conditions, this periodicity has been exploited for generation of DGs. [8,9] Another remarkable feature of the cholesteric mesophase is selective light reflection with the reflection wavelength determined by the simple Equation (1) where n is the average refractive index, and P is the helix pitch. The specific value of helix pitch depends on the chemical structure of the molecules forming the cholesteric phase and concentration of chiral moieties. One of the easiest ways to obtain the cholesteric mesophase is by doping the nematic matrix with chiral components (Figure 1). Variation of structure of chiral molecules by external stimuli leading, for examples, to the photoisomerization, is effectively used for fine tuning of the helix pitch. [10][11][12][13][14][15][16][17] In addition, the application of an electric field also provides a convenient opportunity to change optical properties of the CLC phase. [18][19][20][21] These unique properties enable to design a great variety of optical elements and devices based on CLC layers, films, or cells. Among them it is necessary to mention the media for photo-optical data recording, [22][23][24][25] electrically switchable mirrors, [26,27] optically controllable linearpolarization rotators, [28] coatings with controllable friction and adhesion, [29] materials for display technology, [23,30] secure Modern optics and photonics constantly require break-through materials and designs in order to achieve miniature, lightweight, highly tunable, and effective optical devices. One of the basic optical components is the diffraction grating (DG), widely used for the dispersion of light, beam steering, etc. This review gathers research efforts on diffractive optical elements based on cholesteric liquid crystal (CLC) materials with a supramolecular helical architecture. All main types and fabrication approaches of periodic diffractive structures from CLCs are classified and described. Key optical properties of DGs, their advantages and drawbacks are considered. Special attention is paid on the tunability of DG...

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Direction-tunable cholesteric phase gratings

Cited by 15 publications

References 10 publications

Direction switching and beam steering of cholesteric liquid crystal gratings

Direction switching and beam steering of cholesteric liquid crystal gratings

Stimuli‐Driven Control of the Helical Axis of Self‐Organized Soft Helical Superstructures

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

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