Optical memory, three-dimensional

Spiropyrans show promise for optical recording, three-dimensional optical memories,214 and holography.215 The dyes currently under study for these applications very probably will not be used merely dissolved in a bulk polymer matrix, but will be oriented in films and membranes, or adsorbed or vapor deposited on solid substrates to take advantage of the nonlinear optical properties of the colored forms. For example, thick (0.5 mm) PMMA films of 6-nitro-thiaBIPS can be used to record wavelength-multiplexed volume holograms with an infrared diode laser. This system is impractical at present because of fatigue and poor diffraction efficiencies.216... 

Recently, especially since the LLP phenomenon in SrAl204 Eu, Dy was reported in 1996 [1], LLP materials have been extensively investigated due to its potential application in display in the dark, energy storage, enhancement of the conversion efficiency of solar cell and the fabrication of re-writable three-dimensional optical memory devices, etc [2-5],... 

In this study, a two-dimensional FDTD is performed to simulate the optical field on the metallic nanorod. This method also saves calculation time. In calculating the optical field on a nanoparticle, three-dimensional FDTD should be performed. In this case, the SP excited by both TE and TM modes of the waveguide can be studied. However, PC cluster should also be used to have enough memory to launch the simulation. 

Cuilum, B. M., Mobley, J., Bogard, J. S., Moskovitch, M., Phillips, G. W., and Vo-Dihn, T. Three-dimensional optical random access memory materials for use as radiation dosimeters. And/. Chem. 2000, 72, 5612-5617. 

There are two ways to achieve higher density the extension of the data-recording space in the axial direction, and the reduction of bit size. In this chapter, we describe a method for overcoming the density limit, namely, introduce an additional axial dimension in the recording process. " " The z or longitudinal axis is used in addition to the surface dimension (x—y space) of conventional optical memory. The data are thus written not on the material surface but within the three-dimensional (3D) thick volume. The media that can be used are photochromic materials. ... 

Figure 16.1 shows a principle of bit-oriented three-dimensional (3D) optical memory. A laser beam is focused on a point in a recording medium. Chemical reactions of the medium should be induced at that spot because extremely high intensity is produced at the focus point. By 3D scanning of the focus... 

Three-dimensional optical memory using a new material, urethane-urea copolymer, which contains azo-dyes as a side chain, was demonstrated in 1998. Figurel6.12a shows the chemical structure of urethane-urea... 

Fukaminato, T., Kobatake, S., Kawai, T, and Irie, M. Three-dimensional erasable optical memory using a photochromic diarylethene single cry stal as the recording medium. Proc. Jpn. Acad. 77, B, 30, 2001. 

Three-dimensional (3D) data storage forms a necessity for further computer development. Three-dimensional optical memory with high storage density is a promising technology for increasing the capacity of computer data storage. 

The research in glass modification by use of short laser pulses is driven by scientific interest and their applications have been demonstrated for the formation of three dimensional optical memories and multicolour images , the direct writing of waveguides, waveguide couplers and splitters, waveguide optical amplifier, and optical gratings" ". 

The concept of defects came about from crystallography. Defects are dismptions of ideal crystal lattice such as vacancies (point defects) or dislocations (linear defects). In numerous liquid crystalline phases, there is variety of defects and many of them are not observed in the solid crystals. A study of defects in liquid crystals is very important from both the academic and practical points of view [7,8]. Defects in liquid crystals are very useful for (i) identification of different phases by microscopic observation of the characteristic defects (ii) study of the elastic properties by observation of defect interactions (iii) understanding of the three-dimensional periodic structures (e.g., the blue phase in cholesterics) using a new concept of lattices of defects (iv) modelling of fundamental physical phenomena such as magnetic monopoles, interaction of quarks, etc. In the optical technology, defects usually play the detrimental role examples are defect walls in the twist nematic cells, shock instability in ferroelectric smectics, Grandjean disclinations in cholesteric cells used in dye microlasers, etc. However, more recently, defect structures find their applications in three-dimensional photonic crystals (e.g. blue phases), the bistable displays and smart memory cards. 

Mizuno, T. Yamasaki, K. Misawa, H. Three-dimensional optical memory in a photoacid-induced recording medium. Jpn. J. Appl. Phys., Part 1 2005, 44, 6593-6595. 

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