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Introduction to Smart Polymers
Published in Asit Baran Samui, Smart Polymers, 2022
The polymeric materials for holographic data recording are discussed in Chapter 9. Data recording and reading are performed by optical means and are rigged to the extent that they are not vulnerable to corruption from magnetic and semi-conductor memory. Together with extraordinary high memory, the recording medium can be used for write once and read many times (WORM) and also for the write-erase-write protocol. The basic principle of writing is that the monochromatic laser beam, concentrated on a microspot of the recording medium, changes the physical or chemical properties of the spot. The change occurred allows the spot to be distinguished from the surrounding medium. Irreversible change of the incorporated dye in the recording layer occurs during laser irradiation when making a recordable CD (CD-R).103 In a phase change optical disc, the laser beam-irradiated track portion undergoes crystalline melting, which quenches to an amorphous state after the laser is removed.104 To erase the data, it is irradiated with an erasing laser so that the temperature rises above the crystallization temperature. In this condition, the recorded portion disappears to restores the crystalline phase. After the introduction of photochromism production by the two-photon excitation during the 1970s, it was demonstrated during the 1980s that it could lead to three-dimensional data storage.105 Physical phenomena for data reading and recording have been developed, which were followed by the development of large numbers of chemical systems for the medium. In order to increase the storage capacity, it is possible to incorporate two or even more of these data layers, but the laser interacts with every layer that it passes through when reaching the target layer. Thus, noise is created in another layer. The 3D optical data storage methods overcome this problem by involving nonlinear data reading and writing methods. Practically, a laser is brought to a focus at a particular depth in the recording medium corresponding to a particular information layer. To write the next piece of information, the depth of the focus is changed.
Self-assembling behaviour of new functional photosensitive cinnamoyl-based reactive mesogens
Published in Liquid Crystals, 2020
Alexej Bubnov, Martin Cigl, Nela Sedláčková, Damian Pociecha, Zuzana Böhmová, Věra Hamplová
Generally, the azobenzene-based LCs combine the unique molecular self-organisation characteristic of liquids crystals with the exceptional light-induced response (molecular photo-alignment) of the azobenzene groups [39]. While azobenzene containing high-molecular-mass [39–41] and low-molecular-mass [22,42,43] photosensitive LC materials of various structure and functionality are intensively designed and investigated [44–46] and are even actively used for practical purposes like photoalignment [47]; high-density (volume or 3D) optical data storage devices [48] and other applications [49–51]. Nevertheless, the organic self-assembling materials containing cinnamoyl or other photosensitive moieties are much less considered [52–54]. Light-induced structural chemical transformations in photoactive LC compounds are also very highlighted and desirable. That is why the design and synthesis of new reactive mesogens, especially based on unconventional cinnamoyl group, still remains an actual and highlighted topic. Recently, the photosensitive functional cinnamoyl group has been used for the design LC materials of various shapes, like chiral [55–57] rod-like compounds but also for the discotic [58] and bent-shaped [59–61] LC materials. There are furthermore few cases, when the cinnamoyl group is used for the design of reactive monomers [39,57] and for further grafting them as a side-chain on the polyacrylate or polymethacrylate backbones.
Structural and Optical Coefficients Investigation of γ-Al2O3 Nanoparticles using Kramers-Kronig Relations and Z–scan Technique
Published in Journal of Asian Ceramic Societies, 2021
A. Faraji Alamouti, M. Nadafan, Z. Dehghani, M. H. Majles Ara, A. Vejdani Noghreiyan
Nowadays, the studies on nonlinear optical (NLO) materials with the ultrafast response, enhanced laser-induced damage threshold, larger two-photon absorption (TPA), and third-order nonlinearities have gained increasing interest due to their promising potentials in the next-generation photonic devices including optical switches [15–21], optical information processing [16,17,19–21], 3D optical data storage [17,19–22], optical power limiting [15,16,18–21], optical fiber communication [16,17,19–22], laser-predicated imaging, remote sensing [19–21], frequency conversion of coherent laser sources [17,22,23], optical computing [23], high-density data processing [23], nonlinear imaging [16], image manipulation [15], and color displays [17,23].