HOLOGRAPHIC DATA STORAGE SYSTEM (HDSS)

1. HOLOGRAPHIC DATA STORAGE SYSTEM (HDSS) PreparedBy, Harshil Dave 08-IT-09

2. INTRODUCTION >>Devices that use light to store and read data has always become the backbone of our data storage system for nearly two decades. Each time you access towards the large repository of digital information. >> All the way to the mammoth 320 GB hard disk drives available today, we use also optical devices such as CDs ,DVDs and Blue-Ray Disk . >> With the promise of tomorrow's operating systems and create new era of storage via laser, the demands of being able to quickly store and retrieve enormous quantities of data are ever increasing.

3. DEFINITION • >>Holographic memoryis a technology that can store information at high density inside crystals or photopolymers. • >>Conventional memories use only the surface to store the data. But holographic data storage systems use the volume to store data.

4. BASIC PRINCIPLE OF HDSS >>A hologram is a block or sheet of photosensitive material which records the diffraction of two light sources. >>To create a hologram, laser light is first split into two beams: 1.Source beam- Data signal 2.Reference beam- Carrier signal >>And both intersect on hologram. >> While reading data we hit Reference signal on exact angle which was use during writing process.

6. BASIC COMPONENTS OF HDSS >> BLUE-GREEN ARGON LASER >>POLARIZING BEAM SPLITTERS >>MIRRORS TO DIRECT THE LASER BEAMS >>SPATIAL LIGHT MODULATOR (SLM) >> LENSES TO FOCUS THE LASER BEAMS >> PHOTO -POLYMER >>CHARGE-COUPLED DEVICE (CCD )

7. In a holographic memory device, a laser beam is split in two, and the two resulting beams interact in a crystal medium to store a holographic recreation of a page of data.

8. Implementation

9. WORKING OF HDSS WRITING DATA ON RECORDING MEDIUM >>Light from a single laser beam is split into two beams, the signal beam (which carries the data) and the reference beam. The hologram is formed where these two beams intersect in the recording medium. The object beam, gets expanded so that it fully illuminates a spatial light modulator (SLM) >>The object beam finally interacts with the reference beam inside a photosensitive crystal causing a holograph to be stored

10. Writing Data on HOLOGRAM

11. READING DATA FROM HOLOGRAM >>When reading out the data, the reference beam has to hit the crystal at the same angle that's used in recording the page. The stored interference pattern diffracts the reference beam's light so that it reconstructs the checkerboard image of the light or dark pixels. >> The image is directed upon a charge-coupled device (CCD) sensor array that reads the data in parallel, and it instantly captures the entire digital page. The binary information can now be read from this CCD and the originally stored data is retrieved.

12. Reading Data from HOLOGRAM

13. MULTIPLEXING >>The method of storing multiple pages of data in the hologram is called ‘Multiplexing’. • WAVELENGTH MULTIPLEXING • ANGULAR MULTIPLEXING • SPATIAL MULTIPLEXING > PERISTROPHIC MULTIPLEXING > SHIFT MULTIPLEXING • PHASE ENCODED MULTIPLEXING MULTIPLEXING COMBINATIONS

14. ADVANTAGES OF HDDS >> With three-dimensional recording and parallel data readout, holographic memories can outperform existing optical storage techniques. In contrast to the currently available storage strategies. >>holographic mass memory simultaneously offers high data capacity and short data access time (Storage capacity of about 1TB/cc and data transfer rate of 1 billion bits/second). >> While a defect in the medium for disk or tape storage might garble critical data, a defect in a holographic medium doesn't wipe out information

15. DISADVANTAGES OF HDDS >> Manufacturing cost HDSS is very high and there is a lack of availability of resources which are needed to produce HDSS. >> A difficulty with the HDSS technology had been the destructive readout. The re-illuminated reference beam used to retrieve the recorded information, also excites the donor electrons and disturbs the equilibrium of the space charge field in a manner that produces a gradual erasure of the recording. >> You would be unable to locate the data if there’s an error of even a thousandth of an inch.

16. POSSIBLE APPLICATIONS >> Holographic memory systems can potentially provide the high speed transfers and large volumes of future computer system. >>One possible application is DATA MINING. Data mining is the processes of finding patterns in large amounts of data. Data mining is used greatly in large databases which hold possible patterns which can’t be distinguished by human eyes due to the vast amount of data. >> The many advances in access times and data storage capacity that holographic memory provides could exceed conventional storage and speedup data mining considerably. >> Another possible application of holographic memory is in pet flop computing and most common application is HOLOGRAPHIC VERSATILE DISK (HVD).The future of digital data storage technology.

17. >>Spatial Light Modulator (SLM) Spatial light modulator is used for creating binary information out of laser light. The SLM is a 2-D plane, consisting of pixels, which can be turned on and off to create 1’s and 0’s. An illustration of this is a window and a window shade. It is possible to pull the shade down over window to block incoming sunlight.

18. Holographic Versatile Disc structure1. Green writing/reading laser (532 nm)2. Red positioning/addressing laser (650 nm)3. Hologram (data)4. Polycarbonate layer5. Photo polymeric layer (data-containing layer)6. Distance layers7. Dichotic layer (reflecting green light)8. Aluminum reflective layer (reflecting red light)9. Transparent base HVD

19. Comparison of data storage devices

20. CONCLUSION >> The future of HOLOGRAPHIC DATA STORAGE SYSYEM is very promising. The page access of data that HDSS creates will provide a window into next generation computing by adding another dimension to stored data >> It will most likely be used in next generation supercomputers where cost is not as much of an issue. >> However, many advances in optical technology and photosensitive materials need to be made before we find holograms in our computer systems. Thus we can say that it is new ERA of digital data storage from LASER.

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