Direction switching and beam steering of cholesteric liquid crystal gratings

Jau, Hung Chang; Lin, Tsung‐Hsien; Chen, Yan Yu; Chen, Chun-Wei; Liu, Jui Hsiang; Fuh, Andy Ying–Guey

doi:10.1063/1.3698384

Cited by 38 publications

(30 citation statements)

References 19 publications

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“…b) Diagram demonstrating the intervals of existence of the electro‐induced structures and indicates the correspondence of structure's names which can be found in literature. c) POM images of GM and DM(⊥) cholesteric DGs (at the top) . Computer simulated director field distortion in GM (surface‐frustrated lying‐helix) and DM(⊥) structures.…”

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

“…In ref. , nematic mixture E7 doped with common chiral dopant S811 was introduced to the electro‐optical cell resulting in a d / P 0 ≈ 0.96, which facilitated formation of GM grating. In order to switch the grating direction (i.e., type of the grating, since the lines of GM grating might be only parallel to rubbing direction), a voltage higher than U H was applied followed by abrupt switching off.…”

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

“…Upon dropping the voltage, the transition from homeotropic state to transient planar one was observed. The latter state can be considered as a meta‐stable state (stretched cholesteric helix) and is characterized with the effective pitch P * = ( K 33 / K 22 ) P 0 , which is higher than the native pitch P 0 . Therefore new confinement ratio of the system became ≈0.5 which resulted in formation of DM(⊥) grating upon an applied voltage.…”

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

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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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Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

Section: Diffraction Structures In Clc Materials Induced By Electric mentioning

confidence: 99%

See 2 more Smart Citations

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Ryabchun

Bobrovsky

2018

Advanced Optical Materials

196

106

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“…Beam steering of more than one dimension could be achieved in some optical phased arrays [17][18][19] and cholesteric liquid crystal grating; [16,[20][21][22] however, grating-based deflectors usually suffer from strong dispersion in deflection angle and low deflection efficiency which results from light leakage to other orders of diffraction. Beam steering of more than one dimension could be achieved in some optical phased arrays [17][18][19] and cholesteric liquid crystal grating; [16,[20][21][22] however, grating-based deflectors usually suffer from strong dispersion in deflection angle and low deflection efficiency which results from light leakage to other orders of diffraction.…”

Section: Doi: 101002/adom201600824mentioning

confidence: 99%

Arbitrary Beam Steering Enabled by Photomechanically Bendable Cholesteric Liquid Crystal Polymers

Chen

et al. 2017

Advanced Optical Materials

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Beam-steering technology is now in widespread use in a variety of optical systems, spanning from fiber-optic interconnector to Lidar. Most current techniques are based on optical grating diffractions; they are thus subject to not only finite tuning range, direction, and efficiency but also complex inorganic fabrication and circuit design. A high-degree-of-freedom beamsteering element makes such operations more efficient and versatile. Azobenzene cholesteric liquid crystal polymer (azo-ChLCP) can be regarded as a soft self-assembled Bragg mirror capable of being bent photomechanically. With proper control of pump polarization and exposure time, the output beam can be directly steered to an arbitrary direction. The deflection efficiency was achieved to be at least 90% with an angular tuning range of ≈54°, which is markedly superior to conventional grating-based devices. Additionally, the angle of deflection is independent of wavelength, preventing the deflected beam from spreading out with colors. This work demonstrates and characterizes the azo-ChLCP beam deflector, which features optical tunability, high efficiency, wide tuning range, and polarization-selective deflection direction, making a significant breakthrough in beam-steering technology.

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Stimuli‐Directed Helical Axis Switching in Chiral Liquid Crystal Nanostructures

2018

Functional Organic and Hybrid Nanostructured Materials

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Direction switching and beam steering of cholesteric liquid crystal gratings

Cited by 38 publications

References 19 publications

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Cholesteric Liquid Crystal Materials for Tunable Diffractive Optics

Arbitrary Beam Steering Enabled by Photomechanically Bendable Cholesteric Liquid Crystal Polymers

Stimuli‐Directed Helical Axis Switching in Chiral Liquid Crystal Nanostructures

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