© (2006) Wiley

With increasing demands for data storage, especially in video and imaging applications, new technology is required to obtain higher data-storage capacity. One approach to achieving this objective is three-dimensional optical data storage — significantly increasing data capacity per disk by means of storage in multilayer media. The ability to read or write from a small volume without interference from the rest of the material, referred to as crosstalk, sets a limit on the possible density of data storage. Two-photon absorption effects offer a way of alleviating this crosstalk and have recently been investigated in so-called photochromic materials as they offer data-storage applications both high resolution and sensitivity.

Now, C. C. Corredor and colleagues1 have fabricated a two-photon three-dimensional optical data system using a photochromic polymer. They show that the system is suitable for recording data in thick storage media and for providing a readout method that does not erase existing stored information — they perform 10,000 readout cycles with only a small reduction in contrast. Also, contrary to other techniques, this method allows reading and writing of data at the same wavelength, which is achieved by changing the intensity of the laser light. Although the authors used a relatively expensive femtosecond Ti-sapphire laser to both read and write the information, they suggest that the data could be read using cheaper nanosecond laser diodes with comparable laser intensity, making this high density data-storage system more cost effective.