Holographic Memory

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HOLOGRAPHIC MEMORY

By

Dhruval V. Shah- VESIT

ABSTRACT:

Holographic memory is a technique that can store information at high density insidecrystals. Holographic memory is developing technology that has promised to revolutionalise the storage systems. It can store data up to 1Tb-4Tb in a sugar cube sized crystal. Data from more than 1000 CDs can fit into a holographicmemorySystem. Holographic storage has the potential to become the next generation of storage media Conventional memories use only thesurfaceto store thedata.But holographic data storage systems use the volume to store data. It is based on the principle of holography.This paper provides adescriptionof Holographic datastorage system (HDSS),athreedimensional data storage system which has a fundamental advantage over conventional read/write memory systems. A brief overview of propertiesofhologramswillbe presented first. Applications to computer systems are then covered, with the future of holographic memory presented as a conclusion.

KEYWORDS: Hologram, Holomem

(Holographic Memory).

INTRODUCTION:

Each time you watch a fast-paced DVD movie orpulldownapieceof information from the Internet or even access the ATM at the corner of your street, you are actually tapping into large repositories of digital information. The hard disk, the mainstay of personal and corporate storage, has faithfully obeyed the exponential law. This has happened largely due to increases in aerial density, that is, how many bits are crammed into a square inch. This paper provides a descriptionofHolographic data storage system(HDSS), athree dimensional data storage system which hasafundamental advantageover conventionalread/write. The first stepin understanding holographic memoryis tounderstand what "holographic" means. Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called hologrammemorysystems.A holographic memory is a collection of 3- D holograms, which share a common storage medium volume (the hologram array), and the means to write and read these holograms. As current storage techniques such as DVD reach the upper limit of possible data density (due to the diffraction limited size of the writing beams), holographic storage has the potential to become the next generation of storage media. The advantage of this type of data storage is that the volume of the recording media is used instead of just thesurface. RECORDING DATA:

Like other forms of optical data storage, holographic memoryuseslasersto encode data. It is created with coherent laserlightby interferingthe light transmitted by or reflected from a data pattern (object or signal beam) with an unmodulated carrier (reference beam). The interference pattern created by the interaction of the two beams is captured bya storagemedium, suchasa photopolymer film or an electro-optical crystal (these are referred to as volume phase storage media).Forcertain recording setups and storage medium thicknesses, a 3-D (volume) hologram is recorded, which has useful properties for data storage. By adjusting the reference beam angle,wavelength,or media position,a multitudeofholograms (theoretically, several thousand) can be stored on a single volume.

READING OUT:

The hologram is read out (reconstructed) by illuminating the hologram with only the reference beam. In principal, a perfect 3-D image of the original object is reproduced. The stored data is read through the reproduction of the same referencebeam usedtocreatethe hologram. The reference beam’s light is focused on the photosensitive...
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