Three-dimensional photochromic memory

A summary of BR-based processes and applications can be found in Hampp. Most applications utilize the photochromic properties of BR. Two of these processes are discussed in this chapter the two-dimensional holographic memory and the three-dimensional associative memory. However, other bio-molecular photonic applications are currently being examined. BR is also being used in the process or formation of desahnation of seawater, conversion of sunlight into electricity, artificial retinae, motion detection, optical filtering, neural networking, radiation detection, and biosensor applications. The universal application of BR in many different biomaterials is testament to the flexibility and utility of the protein. 

Toriumi, A., Herrmann, J.M., and Kawata, S., Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope, Opt. Lett., 22, 555-557, 1997. 

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. ... 

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. 

The photoreactivity of DTE derivatives in the crystalline state is of special interest because of their potential usefulness for holographic and three-dimensional memories. In crystals, molecules are regularly oriented and packed in fixed conformations. In many cases, free rotation is inhibited. Therefore, the photoreactivity in the crystalline phase is dependent on the space for free rotation of the thienyl rings and the conformation formed in the crystal lattice. Several reports on the synthesis of metal complexes of photochromic diarylethenes and their photo-reactivity in the single-crystalline phase or the photoswitching of the coordination structure have been reported. These studies demonstrate that complexation to metal ions does not prohibit the photochromic reactions of the diarylethene units in the single-crystalline phase. 

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