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Magneto-Optical Disk Data Storage
Published in Jerry D. Gibson, The Communications Handbook, 2018
A strength of optical recording is that, unlike its magnetic counterpart, it can support read-only, write-once, and erasable/rewritable modes of data storage. Consider, for example, the technology of optical audio/video disks. Here the information is recorded on a master disk, which is then used as a stamper to transfer the embossed patterns to a plastic substrate for rapid, accurate, and inexpensive reproduction. The same process is employed in the mass production of read-only files [CD read only memory (CDROM), and optical ROM (O-ROM)], which are now being used to distribute software, catalog, and other large data bases. Or consider the write-once read-many (WORM) technology, where one can permanently store massive amounts of information on a given medium and have rapid, random access to them afterwards. The optical drive can be designed to handle read only, WORM, and erasable media all in one unit, thus combining their useful features without sacrificing performance and ease of use or occupying too much space. What is more, the media can contain regions with prerecorded information as well as regions for read/write/erase operations, both on the same platter. These possibilities open new vistas and offer opportunities for applications that have heretofore been unthinkable; the interactive video-disk is perhaps a good example of such applications.
Optical information storage and recovery
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Versatility of optical storage is an additional feature of foremost importance for its applicability. Optical recording allows read-only, write-once, and rewritable (erasable) data storage. Read-only optical disks or read-only memory (ROMs) are suitable for distribution of digital contents. In read-only technology, the information is written on a master disk that is then used for printing the embossed patterns onto a plastic substrate. The printing process allows for rapid, low-cost mass reproduction making optical disks the media of choice for distribution of digital data. The write-once read-many (WORM) technology allows one to store permanently a large amount of data on a thin disk medium, to remove it, and to have fast access to it in any compatible optical drive system. Information stored on rewritable optical disks can be erased and rewritten many times. Present optical drives are designed to handle different media formats at the same time—the data stored on read-only, WORM, and rewritable media can be accessed all in one unit.
Magnetic and Optical Recording
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Compared with magnetic recording, optical recording has the intrinsic advantages of superior reliability and portability. However, its performance is inferior due to slower data access time and transfer rate. Another advantage of optical recording, higher areal density, has been disappearing or even reversing to magnetic recording. Both magnetic and optical recording will be continuously improved in the near future, probably toward different applications. Currently, there are some emerging techniques that try to combine the magnetic and optical recording techniques [19], such as amorphous rare earth materials. Table 96.4 is a short list of representative magnetic and optical devices for digital recording.
Thermal kinetics and glass stability criteria of the Se70Te20Cd10 chalcogenide glass
Published in Phase Transitions, 2023
The GFA plays a significant role in determining the use of chalcogenide alloys as recording materials. This is because phase change in optical recording is based on the laser-induced thermal amorphization and crystallization of chalcogenide glasses. The fragility F is an important parameter of GFA because it is a measure of the rate at which the relaxation time decrease with increasing temperature around Tg and is given [38] by where Eg is the activation energy for the glass transition. According to Vigils [38], the values of F for the considered sample were obtained at various heating rates aslisted in Table 1. A glass with bad GFA and low TS indicates memory switching, while threshold switching is found in glasses with good GFA and TS. GFA and TS are important issues in the synthesis of the phase change memory for Ovonic threshold switching and Ovonic memory switching [39]. Moreover, the low values of fragility index F for investigated glassy composition indicate that the glassy Se70Te20Cd10 composition is obtained from the strong glass-forming liquid [38,27].
Synthesis and conjugation properties of alkynyl functionalized salicylidene Ni(II) and Zn(II) phosphine complexes and their use as a precursor for preparation of NiO and ZnO nanoparticles
Published in Inorganic and Nano-Metal Chemistry, 2023
Sagar S. Mohite, Sanjay S. Chavan
Non-linear optical materials exhibiting efficient SHG at shorter wavelengths are important within the field of high-density optical recording, laser printing, optical measurement system, and for other applications.[41,42] Among them, new NLO materials made of metal-organic and coordination networks are a serious point of focus in recent years to judge its potential application as a secondorder NLO material. The non-linear optical properties of the Ni(II) (1a-4a) and Zn(II) (1b-4b) complexes were studied by the Kurtz powder technique and SHG efficiencies obtained are given in Table 4. Comparison of the area of the SHG signal emitted by the sample with the standard urea in the same experimental condition showed that the complexes 1a, 3a, 1b, and 3b and 2a, 4a, 2b, and 4b are ∼0.43 and ∼0.56 times that for urea. The SHG efficiency of and 2a, 4a, 2b, and 4b increases (by a factor of 10–12) by replacing OCH3 by the Br group and are approximately 0.42 and 0.39 times that for urea. No significant effect of the coligands (PPh3 and dppe) was observed on SHG efficiency of the Ni(II) and Zn(II) hybrid complexes. From the results obtained, we may conclude that the substituent’s on the coordinated group plays a major role in charge transfer through the molecule which favors the large second-order polarizability and hence provides a promising strategy to prepare such kind of complexes as a second-order NLO material.
Laser-induced optically modified Se58Ge27Pb15 and Se58Ge24Pb18 thin films
Published in Radiation Effects and Defects in Solids, 2020
The optical properties of laser-irradiated Se58Ge27Pb15 and Se58Ge24Pb18 thin films have been studied using absorption and transmission spectra. Nd: YAG 532-nm laser has been used for sample illumination. Structural characterisation reveals that structure becomes more ordered and crystalline on laser irradiation. This transformation from amorphous to crystalline phase on laser irradiation makes these thin films a promising material for optical recording media. The phase transformation is accompanied by a change in the optical band gap. Significant changes have been observed in band gap, refractive index, extinction coefficient etc on laser irradiation. Band gap is found to decrease on laser irradiation for both the samples. The decrease in band gap is observed due to the increase in the density of states within the band gap region. However, an increase in band gap is observed in the case of Se58Ge24Pb18 thin film at higher illumination time. This may be due to the formation of more heteropolar bonds, which shifts the binding energy of core-level spectra and supports the increase in optical band gap. Refractive index is found to increase on laser irradiation. This is due to the microstructural and chemical ordering in the film. The optical changes in the film can be used effectively for nonlinear optical devices and optical memory devices.