Today`s optical data storage technologies, such as CD, DVD and Blu-ray, use one-photon absorption processes for writing and reading information.
The devices are recorded by pulsing a laser diode to heat areas of a single organic dye layer. The induced heat permanently changes the optical properties of the dye, changing the reflectivity of those areas.
3D writing of a DVD size disk with the picoTRAIN™ GREEN
In contrast, the nonlinear two-photon absorption process can be used to store data within the volume of a disk, thus achieving three-dimensional storage by simply changing the focusing position of the writing beam within the medium. In this fashion it is possible to store hundreds of layers within the volume of a 1-mm thick DVD-type disk.
Layers stored in a WORM memory; layer spacing: 4 microns
The high peak intensities needed for a dominant two-photon absorption process is provided by a picosecond laser at a wavelength of 532 nm. The high intensity in the laser spot locally changes the medium`s properties and thus write a data bit of information. To read this data, the recorded bits are illuminated with a red laser diode that induces fluorescence from the written bits.
