Bit-oriented 3D memory

Multilayered optical rrtemory FIG. 16.1 Principle of bit-oriented 3D memory. 

P. M. Rentzepis et al. first demonstrated a bit-oriented 3D optical memory using a photochromic spirobenzopyran shown in Figure 16.3. Isomer A has an absorption band shorter than 450 nm upon irradiation with ultraviolet (UV) light, it converts to isomer B, which has an absorption band around 600 nm, as shown in Figure 16.4. Isomer B gives fluorescence around 700 nm upon photoexcitation with 500-700 nm light. 

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... 

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