HOLOGRAPHIC DATA STORAGE

Contents

Introduction  Magnetic and conventional optical data storage technologies are approaching physical limits beyond which individual bits may be too small or too difficult to store.  Holographic data storage is an approach of storing information throughout the volume of a medium—not just on its surface.  With the rapidly increasing demand for increased storage capacity in a smaller space, this technology offers an economy in price.

Features  Next – Next generation Technology  1 HVD = 5800 CDs = 830 DVDs = 160 Blu-ray  Media type : Ultra-high density optical disc  Encoding : MPEG-2, MPEG-4 AVC (H.264), and VC-1  Capacity theoretically up to 3.9 TB  Developed by HSD Forum  Usage : Data Storage, : High-defination video and the possibility of Ultra-high defination video  permits over 10 Kbits of data to be read and written in parallel with a single flash

What Is Hologram ? A hologram is a recording of the optical interference pattern that forms at the intersection of two coherent optical beams  Signal beam  Reference beam on the holographic medium.

Types of Holograms Transmission Hologram – Can be used to store data – Uses coherent light Reflection Hologram – The kind you find on credit cards – Uses white light

Holography vs Photography  Black and white photograph – Intensity  Color photograph – Intensity and wavelength  Hologram – Intensity, phase, and sometimes wavelength

Review of Interference

Creating Hologram

Reconstructing the Image

Qualitative Explanation of Storage Reference beamObject imageResultant patternStored in film

Qualitative Explanation of Reconstruction Reference beamStored in filmReflection

Recording Data

Spatial Light Modulator(SDM)  Translates electronic data (0’s and 1’s) into optical pattern of light and dark pixcels  Data is arranged in an array similar to a checker board of usually 1 million bits  By varying the angle of the reference beam,wavelength or media position, many holograms can be stored in the same volume of storage material

Reading Data

Pattern Left on Media

HVD Technology  HVD uses a technology called ‘collinear technology’  Two Laser rays one blue-green and one red are used  The role of blue-green laser is to read the data encoded the form of laser interference fringes from the holographic layer  The red laser serves the purpose of a reference beam and also to read the servo info from the aluminum layer

Read only HVD Read\Write HVD  supports some irreversible photochemical reaction triggered by the bright regions of the optical interference pattern  Material diffuses from darker to brighter regions so that short monomer chains can bind together to form long molecular chains  uses inorganic photorefractive crystals  Electrons get photo- excited at the bright fringes, diffuse or drift and are re-trapped at a dark fringe  Trapped charge can be rearranged by later illumination, so it is possible to erase recorded holograms

Current State of Technology  Storage and Cost – CD-ROM: 783 MB to 1.3 GB – 10 cents – DVD+DL: 5 GB to 30 GB - $3 – Blu-Ray DL: 25 GB to 50 GB - $30 – InPhase Tapestry: 300 GB - $250 – Hard disk: 1 TB - $300 – HVD (future): 4 TB

Current State of Technology  Tansfer rates and Recordable Player Approx Cost – CD-ROM 52x: ~ 5 MB/second --$200 – DVD 16x: ~ 20 MB/s --$ 2000 – InPhase Tapestry: 20 MB/sec – Blu-Ray and HDDVD: ~ 30 MB/sec --$2000 – 7200 rpm Hard disk: 80 MB/sec – HVD: 1 GB/sec --$3000

Interesting Facts  It has been estimated that books in the U.S. Library of Congress, the largest library in the world, could be stored on 6 HVD’s  The pictures of every landmass on Earth – like the one shown in Google Earth can be stored on two HVD’s  With MPEG4 ASP encoding, a HVD can hold anywhere in between 4,600 to 11,900 hours of video, which is enough for non-stop Playing for a year