Cholesteric Gratings Doped with a Dichroic Dye

Fuh, Andy Ying–Guey; Lin, Chi Huang; Hsieh, Ming‐Feng; Huang, Chi Yen

doi:10.1143/jjap.40.1334

Cited by 16 publications

(6 citation statements)

References 15 publications

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“…[3][4][5] The self-assembling characteristics of CLCs enable easy fabrication. The stripe direction of CLC gratings has also attracted the interest of researchers.…”

mentioning

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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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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“…[3][4][5] The self-assembling characteristics of CLCs enable easy fabrication. The stripe direction of CLC gratings has also attracted the interest of researchers.…”

mentioning

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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“…It is known that the application of an electric field leads to untwisting of the cholesteric helix (i.e., P growth). An increase in the applied field above the threshold ( U TH ) for a GM grating leads to an increase in the grating period and, this growth continues until the field value reaches the threshold voltage of the transition to a homeotropic state ( U H ) . In this case, the diffraction efficiency of a GM grating varies insignificantly and only in regions close to the transition to a homeotropic state.…”

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Ryabchun

Bobrovsky

2018

Advanced Optical Materials

185

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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“…2019, 31, 1806172 and switch the stripes. One of the first examples of dual stimuli CLC gratings was reported by Fuh et al [275] A CLC mixture was doped with a dichroic guest-host dye (2 wt%) and the sample was filled into a slab cell previously treated for inducing planar alignment. The dye absorbs the light of a pump beam and consequently induces temperature change.…”

Section: Dual Stimuli-driven Cholesteric Lc Gratingsmentioning

confidence: 99%

Dynamic Control of Light Direction Enabled by Stimuli‐Responsive Liquid Crystal Gratings

et al. 2018

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the duality consolidation, the idea of controlling light and how it interacts with matter has always been an exciting topic. Visible light, as we perceive it, is a small portion of the electromagnetic spectrum composed of mutually perpendicular oscillating electric and magnetic fields that propagate through space and presents wave-like and particle-like behavior. Since the elements comprising matter possess dynamic electron clouds, the electromagnetic nature of light prompts different responses when it interacts with different materials, depending on its intensity, frequency, the arrangement of molecules, and so on. Whenever light interacts with matter, it might be absorbed, re-emitted, scattered, or transmitted. Although these effects are well known, the combination of them with new, innovative materials pushes optics forward. In fact, advances in optics have often occurred through the development of materials with improved optical properties, thus creating remarkable applications that tremendously influence our daily lives. These exciting applications include image processing and recording, lasing, data storage, display devices, detector systems, propulsion systems, and optical tweezers, which have enabled remote micromanipulation of colloidal particles and promising applications in various biomedical and biological applications. [1][2][3] There is, however, one component that stands out: the diffraction grating. It is generally regarded as one of the most important devices in the development of several fields of science. [4] Such importance comes from the fact that a diffraction grating is a device with a periodic structure capable of changing the propagation and splitting the spectrum The ability to control light direction with tailored precision via facile means is long-desired in science and industry. With the advances in optics, a periodic structure called diffraction grating gains prominence and renders a more flexible control over light propagation when compared to prisms. Today, diffraction gratings are common components in wavelength division multiplexing devices, monochromators, lasers, spectrometers, media storage, beam steering, and many other applications. Next-generation optical devices, however, demand nonmechanical, full and remote control, besides generating higher than 1D diffraction patterns with as few optical elements as possible. Liquid crystals (LCs) are great candidates for light control since they can form various patterns under different stimuli, including periodic structures capable of behaving as diffraction gratings. The characteristics of such gratings depend on several physical properties of the LCs such as film thickness, periodicity, and molecular orientation, all resulting from the internal constraints of the sample, and all of these are easily controllable. In this review, the authors summarize the research and development on stimuli-controllable diffraction gratings and beam steering using LCs as the active optical materials. Dynamic gratings fabricated by applying external f...

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Cholesteric Gratings Doped with a Dichroic Dye

Cited by 16 publications

References 15 publications

Direction switching and beam steering of cholesteric liquid crystal gratings

Direction switching and beam steering of cholesteric liquid crystal gratings

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Dynamic Control of Light Direction Enabled by Stimuli‐Responsive Liquid Crystal Gratings

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