Storage optical

Photochromic compounds could possibly be used for rewritable optical storage materials. This is one of the reasons for the widespread current interest in photochromies. Hirshberg is the first person who suggested that a photochromic compound could be used as an optical data storage material. Heller et a .3 summarized the basic requirement of photochromic compounds for rewritable optical storage materials. 

The coloration and bleaching processes consist of irradiation with UV light and a 632.8-nm laser, respectively. After five hundred written-erased cycles on the photochromic disk sample, there was no change that could be observed in the photosensitivity and other properties of the disk. The sample was stored at ambient conditions for over 5 years with its optical properties well preserved. 

According to laser photolysis results, the time scale of the coloration of heterocyclic fulgides is shorter than a few nanoseconds and extends to the picosecond time scale. The results indicated that the photoresponse of the photochromic optical disk could be very fast. 

The bleaching quantum yield of compound 57d irradiated at 550 nm is about 0.00043. When the irradiation wavelength is moved over 750 nm, the quantum yield 

Another potential method had been suggested. The basic idea is that the wavelength of the detection beam is outside the absorption band of the colored form of the photochromic compound. Wilson showed that the difference in the refractive indices between the two states of the photochromic fulgides in the near-infrared region could be used as a detection method. 

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Optical storage disks Optical storage media Optical switches Optical trapping Optical tweezers Optical wave guides... 

Polymers are only marginally important in main memories of semiconductor technology, except for polymeric resist films used for chip production. For optical mass memories, however, they are important or even indispensable, being used as substrate material (in WORM, EOD) or for both substrate material and the memory layer (in CD-ROM). Peripheral uses of polymers in the manufacturing process of optical storage media are, eg, as binder for dye-in-polymer layers or as surfacing layers, protective overcoatings, uv-resist films, photopolymerization lacquers for repHcation, etc. 

Besides the estabUshed audio CD and CD-ROM, there are other variants of optical storage disks with imprinted information which differ in the way the data are processed. 

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. 

Coatings for optical storage. Most of these coatings are processed by sputtering or evaporation but MOCVD is being actively considered. 

Hurditch, R. Dyes for optical storage disc media. Chemichromics 99, New Orleans, January 27-29, 1999. 

CD-R was something of a surprise invention as, in the late 1980s, most of the major manufacturers in the optical memory area were commercializing the non-standard and relatively expensive WORM media, while focusing their research and development efforts on erasable optical storage. It was also believed that a writeable CD-Audio/CD-ROM-compatible medium was not feasible, due to the high reflectivity needed to meet the CD standard as defined by the Red and Orange Books.196... 

The indole- and benzindole-cyanine dyes illustrated in Scheme 6 are used by many major manufacturers in optical disk recording applications. These types of dye tend to be more light-stable than many other readily synthesized polymethine dyes. To increase the photostability, the dyes are used in combination with various types of stabilizers such as nickel dithiolato complexes and selected tertiary aromatic amine compounds.199 The application of cyanine dyes for optical storage media was primarily developed in Japan203 and several dyes and compatible stabilizers are commercially available in pure form from Japanese suppliers.199... 

Two naphthalocyanine derivatives (Scheme 9) were mixed together to improve read-out stability in a write-once optical storage system.220 The Ge derivative has a bulky structure with large side chains on the central atom, whilst the Cu derivative has a flat structure. The stability of the medium under 1 mW laser irradiation for read-out was improved 100-fold compared to that of a single-component system.220... 

Shen, S. Liu, K. Huijun, X. Gu, D. Tang, F. Chen, Q. Spectroscopic properties of phthalocyanine dyes for optical recording medium. Proc. SPIE Vol. 2931, 73-77. Fourth International Symposium on Optical Storage (ISOS 96), Gan, F.X., Ed. 

Fuxi, G. Tao, L. Optical properties and recording characteristics of phthalocyanine-derivative LB films. Proc. SPIE Vol. 2053, 95-105. Optical Storage Third International Symposium, Fuxi, G. Ed. 

Giitlich and Hauser (1989) Thermal and light-induced spin crossover in iron(II) complexes—new perspectives in optical storage [227]. 

C Wang, H Fei, Y Qiu, Y Yang, Z Wei, Y Tian, Y Chen, and Y Zhao, Photoinduced birefringence and reversible optical storage in liquid-crystalline azobenzene side-chain polymers, Appl. Phys. Lett., 74 19-21, 1999. 

Optical Storage and Retrieval Memory, Neural Networks, and Fractals, edited by Francis T. S. Yu and Suganda Jutamulia... 

With commas A novel, inexpensive biosensor was used to measure calcium. Without commas There are no reports on the optical storage luminescence exhibited by this important industrial phosphor. (From Dhanaraj et ah, 2001)... 

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

Blue lasers allow higher resolution, and hence higher density of optical storage of information, on devices such as DVDs than the infrared GaAs lasers allow. The earliest blue lasers were based on ZnSe but their lifetime proved too short for commercial applications. Lasers based on gallium nitride (GaN), first demonstrated in 1995, have proved to have greater lifetimes. In these lasers, the photons are produced not in a bulk semiconductor but in quantum wells. 

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