Optical storage media

The problem with the application of these changes in optical properties for optical data storage is that the significant drop in reflectivity upon the first UV irradiation is related to an irreversible structural change. So the film can be used a as write-once medium only. Furthermore, the sensitivity of the system is low, so writing the information takes a rather long time. The changes in the optical properties in subsequent irradiation cycles are reversible, but they are connected with the unstable cis-isomer, which renders the inscribed information volatile. 

Figure 3.88. Composition of a multilayer optical data storage medium photosensitive layer of about 1-p.m thickness (1), nonphotoactive polymer as separating layer of 30-pm thickness (2), and glass substrate (3) [244],...

Liu C, Dutton Z, Behroozi CH et al. Observation of coherent optical information storage in an atomic medium using halted light pulses. Nature (London) 2001 Jan 25 409 490-493. 

Vo-Dinh, T Stokes, D. L. SERODS a new medium for high-density optical data storage. Proc. SPIE-Int. Soc. Opt. Eng. 1998, 3401, 284-290. 

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... 

---