Optical data storage in photosensitive glasses and spin state transition compounds

Matthieu Bellec (1) , Lionel Canioni (1) , Arnaud Royon (1) , Bruno Bousquet (1) , Jérôme Degert (1) , Eric Freysz (1) , Thierry Cardinal (2) , Jean-François Letard (2)

1 CPMOH - Centre de physique moléculaire optique et hertzienne
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Up to now, the common media for optical data storage are the discs (blue ray technology for example). However, by definition, this technology is limited to two dimensions. The necessity for increasing data storage capacity requires the use of three-dimensional (3D) optically based systems. One of the methods for 3D optical data storage is based on volume holography. The physical mechanism is photochromism, which is defined as a reversible transformation of a single chemical species between two states that have different absorption spectra and refractive indices. This allows for holographic multiplexing recording and reading, such as wavelength (Rakuljic et al., 1992), angular (Mok, 1993), shift (Psaltis et al., 1995) and phase encoding. Another promising 3D optical data storage system is the bit-by-bit memory at the nanoscale (Li et al., 2007). It is based on the confinement of multi-photon absorption to a very small volume because of its nonlinear dependence on excitation intensity. This characteristic provides an income for activating chemical or physical processes with high spatial resolution in three dimensions. As a result there is less cross talk between neighbouring data layers. Another advantage of multi-photon excitation is the use of infrared (IR) illumination, which results in the reduction of scattering and permits the recording of layers at a deep depth in a thick material. Two-photon 3D bit recording in photopolymerizable (Strickler & Webb, 1991), photobleaching (Pan et al., 1997; Day & Gu, 1998) and void creation in transparent materials (Jiu et al., 2005; Squier & Muller, 1999) has been demonstrated with a femtosecond laser. Recording densities could reach terabits per cubic centimeter. Nevertheless, these processes suffer from several drawbacks. The index modulation associated with high bit density limits the real data storage volume due to light scattering. The fluorescence can limit the data transfer rate and the lifetime of the device.

Domaines: Matériaux; Optique / photonique

Matthieu Bellec, Lionel Canioni, Arnaud Royon, Bruno Bousquet, Jérôme Degert, et al.. Optical data storage in photosensitive glasses and spin state transition compounds. Florin Balasa. Data Storage, InTech, pp.33-51, 2010, 978-953-307-063-6. ⟨10.5772/8874⟩. ⟨hal-00609299⟩