Lasers can make storage on optical media more denser

Ontario based University researchers have found a novel way to use laser to store and retrieve data from conventional optical discs, such as DVDs and Blu Rays, without the need for special preparatory steps. The scalable technique stores info bits in a multilayer structure using the 3D volume of disc, and ultrafast lasers are used to keep the changes in the disc on a micron scale.

The new technology will help in using the current conventional discs be transformed into ultrahigh capacity storage media by encoding multilevel and multiplex information within the 3D volume of the recording medium. However, in most cases the recording medium must be photosensitive, which requires doping with photochromic molecules or nano particles.

In order to exploit 3D optical data storage capabilities without the need for dopants, researchers at the University of Ottawa used a pulsed laser to record data in micron-sized modified regions of a disc. Upon excitation by the read laser, each modified region emitted fluorescence. The fluorescence moieties induced by the laser demonstrated different emission profiles upon excitation at different wavelengths. The researchers correlated the intensity of the fluorescence signal with the energy of the recording laser and used this to assign 32 grey levels, corresponding to five bits of data.

Around 20 layers of embedded data was demonstrated by research team and it was done by tailoring the read laser power and detector sensitivity, the number of layers in a conventional optical disc that could be imagined without loss of information. Scientists say that the 20 layers of embedded data can be increased to 30 soon. Similar results were obtained using different excitation lasers and discs made from different types of plastic, including polydimethylsilozane (PDMS), Polystyrene (PS) and Polycarbonate (PC).

The flexibility provided by this technique enables data to be stored in commonly available plastics and makes data accessible at any excitation within the visible spectrum. The stored data can be embedded in the bulk material and is thermally stable up to the glass transition temperature of the recording medium, thereby offering a long shelf life and eliminating the need for the recording medium to be photosensitive.

Storage capacities of up to 0.2 terabytes, scalable up to 0.5 terabytes, were demonstrated. Higher storage capacities could potentially be achieved by overcoming the diffraction limit of light to record data on a submicron scale.

Reduction of fluorescence signal can lead to loss of information, but this can be easily recovered by increasing the detector sensitivity and/or the power of the read laser.

Optical discs are a practical medium for long-term data storage, which requires stability and integrity at relatively low cost. Storing information bits in a multilayer structure using the 3D volume of a disc can overcome the limitations of the planar technology of optical discs and provide ultrahigh storage capacities.

The researchers are planning to increase the R/W capabilities of optical discs further to such an extent that they can be arranged in an array and be used as an appliance to store data( like how facebook is using Blu ray disc populated storage appliances). If the access capability gets improved, then the arrays can be used as low cost NAS appliances by SMBs.

So, will all this experimentation challenge Scale out NAS technology? That’s never going to happen with the way the development is taking place on current note.

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