Optical storage devices

The limitation to disk constmctions with a laser beam reflected at the disk surface is a large drawback, however. This prevents the insensitivity against dust and dirt, which is well known from current optical storage devices with a laser beam reflected after penetration of the transparent substrate. 

Polycarbonates find use as amorphous thermoplasts in nonbreakable windshields, housings for electric and electronic equipment, and as substrate in optical storage devices (CD, DVD). 

CD-ROM Acronym for compact disc read-only memory. A high-capacity, optical storage device that uses compact disc technology to store large amounts of information, up to 650MB (the equivalent of approximately 300,000 pages of text), on a single 4.72" disk. 

Side-chain LCPs can be prepared by attaching a mesogen pendant to a flexible polymer backbone (18). These materials often have optical properties similar to low molar mass LCs and have generated interest for such applications as non-linear optics, filters and optical storage devices. 

The major applications of lasers are CD players, optical storage devices including CD-ROM (optical read-only memory), WORM (write once, read many times) and true optical disks (unlimited read and write). The amount of information that can be packed on a disk presently is limited to the size of the spot generated by the laser. The shorter the wavelength, the smaller the spot. Other applications include laser printers, spectroscopy, and communications. Lasers operating at 1.3 micrometers and 1.55 micrometers are used for low loss quartz fiber optic communications. AlGaAs is used for... 

Frequency doubling, or SHG, as illustrated in Figure 1, is of keen interest as a means of generating new laser sources. Frequency doubling of low power diode lasers from the red or infrared into the blue comprise a prime commercial application. Device outlets include higher capacity optical storage devices, as well as more sensitive laser printers and copiers. The objective is to increase not only the molecular response p, but of course the material response Be-... 

Individual customers can access selected parts of the Beilstein database with their own microcomputers when attached to a Winchester or Optical Storage Device (CD-ROM). 

The use of self-assembled QDs has also been discussed as the basis of an all-optical storage device in which excitons are optically generated and the electrons and holes are stored separately in coupled QD pairs [133]. By applying an electric field, the electron and hole could be forced to recombine so as to generate a photon which would provide an optical read-out. 

Our approach reported recently has been somewhat different. For a number of years we have also believed that the main potential for polymer liquid crystals would be in optical storage devices. 

Both the dark and bright states of the SSFLCs shown in Fig. 5.1.4 are stable after an electric field is removed. This memory effect is a result of the surface anchoring effect and the fact that both states are elastically equivalent. The memory effect is very important for high multiplexing of displays in order to avoid the drawback of crosstalk, and to obtain an optical storage device. 

One of the most promising potential uses of liquid crystal polymers is in optical storage devices [133, 135]. The information is written using a He-Ne laser. Images are stable over a long period of time (at least 4 years under ambient conditions), and are erasable by applying an electric field. The absorption of the laser beam is facilitated by incorporating a dye into the polymer [136]. 

P. O. Astrand et al., Five-membered rings as diazo components in optical storage devices an ab initio investigation of the lowest singlet excitation energies, Chem Phvs Letters 325. 115 (2000). 

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