Analyses of bit-oriented optical memories using photochromic media

Using a simple model we estimate the achievable characteristics of bit-oriented optical memories using photochromic recording media. For readout by sensing the absorption of the medium, which will degrade the stored information, the required write energy per bit is of the same order as or lower than that for common ablative or pit-forming write-once media, and the required sample concentration appears to be achievable. To be able to erase at the same rate as data are written, the erase source must have a power output as much as an order of magnitude greater than that of the write source, and this may present a serious problem. For readout by sensing the refractive-index change in the medium, to achieve a nondegradative readout, the required erase exposure and sample concentration both appear to be impractically large.