A Dynamic Grating Using a Photochemical Phase Transition of Polymer Liquid Crystals Containing Azobenzene Derivatives

Hasegawa, Makoto; Yamamoto, Takahiro; Kanazawa, Akihiko; Shiono, Takeshi; Ikeda, Tomiki

doi:10.1002/(sici)1521-4095(199906)11:8<675::aid-adma675>3.0.co;2-z

Cited by 65 publications

(35 citation statements)

References 4 publications

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“…In this part of the polymer film an isothermal transition from the chiral nematic to the isotropic state takes place. Such an isothermal phase transition had been reported for nematic polymers previously by Ikeda et al [34][35][36]. Obviously a thin isotropic layer is formed close to the upper glass plate.…”

Section: Discussionsupporting

confidence: 76%

“…The homogeneous planar texture is destroyed by UV irradiation; the UV irradiation leads to E-Z photoisomerization of azobenzene units the Z-isomer tends to act as a nonmesogenic additive due to its bent shape, and thus destroys the mesophase structure (figure 13) [34][35][36]. We can expect that most of the Z-isomers produced are located in the top layer oriented towards the irradiation source, since the absorbance of the copolymer film is very high at 365 nm (more than 2).…”

Section: Discussionmentioning

confidence: 99%

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Photoinduced textural and optical changes in a cholesteric copolymer with azobenzene-containing side groups

et al. 2004

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Textural changes induced by UV irradiation of planarly oriented films of a cholesteric copolymer were investigated. The copolymer is composed of photosensitive ethoxyazobenzene and chiral cholesterol-containing side groups, and displays a chiral nematic phase with a left-handed helical supramolecular structure in the temperature range 84-128 ‡C. UV light with a wavelength of 365 nm leads to a deformation of the planar texture at temperatures higher than 100 ‡C and to a reduction of the absorbance peak for left-handed circularly polarized light. Polarizing optical microscopy revealed the formation of a focal-conic texture in the irradiated regions. The texture induced by irradiation is very stable but the initial planarly oriented state can be recovered by mechanical stress. The observed phenomenon is attributed to the E-Z photoisomerization of azobenzene groups leading apparently to the formation of a thin isotropic layer in the films which in turn causes a destabilization of the planar texture. At temperatures below 100 ‡C the textural transformations are accompanied by small shifts of the selective reflection maxima to longer wavelengths. The kinetics of the observed phenomenon were studied in detail and the influence of different parameters, such as light intensity and temperature, examined.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Photoinduced textural and optical changes in a cholesteric copolymer with azobenzene-containing side groups

et al. 2004

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“…We succeeded in rapid optical control of grating formation by switching writing beams in PLCs containing azobenzene moieties with strong electrondonating and electron-accepting groups at 4,4'-positions, in which the azobenzene moieties act simply as photoresponsive chromophores, to induce the thermal I to N phase transition effectively. 17,18 A large change in the refractive index (ca. 10 22 ) was also induced in thin ®lms (ca.…”

Section: Introductionmentioning

confidence: 99%

Holographic gratings and holographic image storage via photochemical phase transitions of polymer azobenzene liquid-crystal films

et al. 2000

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Phase-type gratings formed by photochemical phase transitions of a polymer azobenzene liquid crystal have been characterized. The sensitivity of the material was improved by a factor of 23 in the liquid-crystalline phase owing to effective induction of the photochemical phase transition in the bright fringes of the interference pattern. A mechanism for grating formation in ®lms based on dynamics both in grating formation and for the photochemical phase transition has been proposed. Observation of the grating structure with a polarizing optical microscope con®rmed that the isotropic phase induced photochemically was arranged at well de®ned separations. The polymer azobenzene liquid crystal showed a storage capability of w100 Mbits cm 22 which corresponds to a resolution of v1 mm and a spatial frequency of w1000 lines mm 21 . We also attempted holographic image storage using a photomask as an object.

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“…[147] Dynamical control using holographic method was also demonstrated with polymer LCs containing azobenzene derivatives capable of cis-trans isomerization, [148] switching on and off the grating by turning on and off the writing beam. For instance, PDLCs need relatively high fields to switch and present quite large light scattering.…”

Section: Polymer-based Nematic 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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A Dynamic Grating Using a Photochemical Phase Transition of Polymer Liquid Crystals Containing Azobenzene Derivatives

Cited by 65 publications

References 4 publications

Photoinduced textural and optical changes in a cholesteric copolymer with azobenzene-containing side groups

Photoinduced textural and optical changes in a cholesteric copolymer with azobenzene-containing side groups

Holographic gratings and holographic image storage via photochemical phase transitions of polymer azobenzene liquid-crystal films

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

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