Peter Török's research group - Research Topics

Optical data storage

Researchers: C. Macías Romero, G.-H. Ho, B. Eastley, M. Foreman, P.R.T. Munro, A.S. van de Nes and P.Török

Related projects:

• Multiplexed ODS
• Multiplexed ODS - writing techniques
• Rigorous modelling of ODS
• Information theory aspects of ODS

 “Optical data storage” is a general term covering all data storage techniques that use optical means to read, write and/or erase data. These include CD, DVD and even magneto-optical disks. DVDs have come a long way since the original introduction of CDs, the former being in essence a high density counterpart of the latter (see figure on the right). CDs are able to store 670MB of information whereas DVDs can store up to 2.4GB data per layer. This corresponds to a storage density increase of 3.6 times which was achieved partly by decreasing the wavelength of the laser used to illuminate the disk and partly by increasing the numerical aperture of the lens employed.

The “new technology” which is currently being introduced to the market is the so-called BluRay system which, in principle, have the capability of 100GB+ data storage per layer.  This represents the theoretical limit to what can be achieved by conventional optical means, i.e. by further reducing the wavelength (405nm) and increasing the numerical aperture (0.85).

We have already constructed the model for describing the optical system of a BluRay DVD. Simulations are carried out by means of combination of analytic and rigorous numerical methods. Details of this model and some of our theoretical results can be found here.

Traditionally, mainly due to digital noise considerations, optical data storage devices used a single pit to store one bit of information. However, our current optical and electronic means are advanced enough to be able to compromise on this point and encode a single pit by more than a bit information. This method in principle has the capability of increasing the data storage density to over 1TB (1000GB) per layer. The method is denoted Multiplexed Optical Data Storage (MODS). Current writing techniques will not be applicable for MODS, and new methods are currently being studied. The theoretical limits of such an approach are also studied from an information theory point of view. This method can be used as an alternative to traditional means of achieving super-resolution.

A "White paper" has been produced in consulatation with many European universities and industrial companies on the future of Optical Data Storage which can be found here.

To become involved in this project please contact Dr Peter Török.

This project is funded by the EPSRC, Plasmon and the British Council.

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