Optical rewritable technology

Figure 4.9 In-cell LC twist angle change during exposure process with 125 mW/cm polarized light of high-pressure Hg lamp filtered at a peak of 440 nm [44]. The polarization angle was selected to obtain saturation for 12° and 62° LC twist angles. Reproduced from A. Muravsky, A. Murauski, X. Li, V. Chigrinov, and H.-S. Kwok, Optical rewritable liquid-crystal-alignment technology. Journal of the SID 15/4, 267-273, The Society for Information Display...

Figure 6.14 Microscopic picture of assembled LC-clad photonic chip in reflected non-polarized light. Left without alignment layer (with schlieren structure). Right with azo-dye SDl photoalignment layer on bottom substrate [26]. Reproduced from A. Muravsky, Optical rewritable photoalignment technology application in photonics and displays. PhD thesis proposal, HKUST (2008)...

A. Muravsky, Optical rewritable photoahgmnent technology application in photonics and displays. PhD thesis proposal, HKUST (2008). 

Other Imaging Materials. Photopolymer technology is being utilized in the manufacture of other types of optical elements including rewriteable recording materials (e.g. photochromic imaging) (59) and permanent information recording by processes such as laser ablation. 

Other dye-based technologies evaluated for optical data storage include photo-chromic dyes for rewritable systems and azo dyes for holographic data storage. Spirobenzothiopyran dyes such as (40) absorb in the red/near-IR in their colored form and are suitable for erasible optical data storage [34]. Dyes for holographic data storage, such as (41), are similar to those used in nonlinear optics [35] (see below). 

Ultrashoit-pulsed lasers are efleetive, but are not a practical solution for an optical data storage system. It is possible to achieve a three dimensional rewritable bit data storage using continuous wave illumination. With this technology an information density of 88 Gbitcm could be achieved. 

The earliest writable optical drives were, in fact, WORM drives, and although the rewritable drive is more popular for daily storage needs, the WORM technology has a clear place in data storage because it allows permanent archiving capability. 

---