Details of Grant 

EPSRC Reference:	EP/C528905/1
Title:	Terabyte non-volumetric optical data storage by multiplexing
Principal Investigator:	Török, Professor P
Other Investigators:
Researcher Co-Investigators:	Mr P Munro
Project Partners:
Department:	Physics
Organisation:	Imperial College London
Scheme:	Standard Research (Pre-FEC)
Starts:	01 October 2005	Ends:	30 September 2008	Value (£):	364,333
EPSRC Research Topic Classifications:	Optical Communications Optical Devices & Subsystems
EPSRC Industrial Sector Classifications:	Communications Electronics
Related Grants:
Panel History:
Summary on Grant Application Form
Albert Einstein said Information is not knowledge. If this were false then, owing to the enormous amount of information that we currently create, there would be very little left unknown about the world. According to researchers at the University of California, Berkeley, the world currently produces the equivalent of approximately 800 MB of information per person per year.Optical data storage is now a long established technology which has been used for over 20 years, primarily as a read only data storage. During this time we have seen the introduction of the CD, DVD and imminently, the BluRay disk. Each one has lead to successively increased storage capacity. This progression has been achieved by reducing the size of the pits used to encode data onto the disk.The process of miniaturisation is limited however. This is because the spot size of the focused beam of light used to read the disk must also be reduced and this is fundamentally limited. The spot size depends upon the wavelength of light and the focusing power (called the numerical aperture) of the focusing lens. Both of these limits have been reached and so a new approach is required to further increase the capacity of an optical disk.The aim of our project is to increase the capacity of an optical disk through multiplexing. This means that we will replace typical pits with a slightly more complicated feature. Each feature will store more than just a single bit of information. In order to achieve this, each feature will have an angular dependent property and the information will be encoded in the angle of the feature. For example, we have successfully demonstrated that by positioning a step within a pit, the angle of the step may be used to store information. The data storage capacity of such a disk would depend primarily upon how many different step angles we can reliably detect. Such a detection process is made possible because of an intrinsic property of light known as polarisation. Polarisation refers to the direction of the vibrations which make up light waves. This vibration is always in a direction perpendicular to the direction that a light wave is traveling. We have demonstrated that the pattern of light reflected by a pit with an angled step depends strongly upon the angle of the step relative to the angle of the direction of polarisation of beam used to read the disk. We have in fact shown that a novel optical system may be used to determine very accurately the angle of the step.In order to develop the system we have established three objectives for the project. The first objective is to design and analyse the best pit configuration. For this objective we will analyse different pit designs and also study how each pit design may be optimized to enhance its effectiveness. The second objective will be to design a beam to most effectively read the disk features. Such a beam must have polarisation properties which will allow the angular feature of the pit to be read. It must also have the property of minimising the effect of adjacent pits during the reading process. The final objective will be to design, analyse and build a prototype read-out system. This will be the ultimate test of the system.Initial investigations of this system suggest that we may be able to store 1 Terabyte (1024 Gigabytes) onto a single disk. Such a disk will be very useful in archiving applications like for example libraries and business record keeping. It will also be useful to the film industry which seeks higher capacity storage media to store films with ever increasing data size. These are however only a couple of examples, one only needs to look at how data storage requirements have increased over the last decade in order to estimate how they will change over the next decade. Modern day trends will thus necessitate the development of a disk like that proposed.
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Organisation Website:	http://www.imperial.ac.uk