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From CD to Blu-ray Disc: The History of Optical Storage Device
Transcript of From CD to Blu-ray Disc: The History of Optical Storage Device
In the middle layer of a disc, there is a flat light reflecting layer called "land"
many "pits" written in a spiral-shaped track From CD to Blu-ray Disc:
The History of Optical Storage Device Lau Wai Chung
Lau Tsz Ki Content How disc works Aluminium Gallium Arsenide (CD) Recent Development Laser Disc Laser pits land http://www.laesieworks.com/digicom/Storage_CD.html Zine Blende Structure Advantage and Disadvantage Crystal Structure 5.6533 + 0.0078x A Aluminum Gallium Arsenide
Zine blende structure with some Ga atoms replaced by Aluminium Aluminium
OR Gallium Arsenide Band Structure First Brillouin Zone Face-centered cubic body-centered cubic 1.42eV<band gap<2.16eV depending on the proportion of Al FCC Lattice with 2 atoms decorating one lattice point Direct band gap. No additional "collision" with phonon is needed. The band gap is of the size 1.42eV to 2.16eV , which is ranged from near infra-red (~800nm)to green(~550nm) depending on the proportion of the Al. High flexibility of controlling the wavelength. HAZARD: AlGaAs is toxic and is irritating to skin,eyes and lungs! Aluminium Gallium Indium Phosphide (DVD) Ga/Al/In Phosphide First Brillouin Zone Zinc Blende structure Band Structure Face-centered cubic Crystal Structure Advantage and Disadvantage body-centered cubic Gallium Nitride (BRD) AlGaAs is widely used in CD-drive and fibre-optic communication. Wurtzite Structure Advantage Nitride hexagonal closed pack Gallium Wurtzite structure a = 3.189 A
c = 5.178 A Crystal Structure a c HCP Lattice with 2 atoms decorating one lattice point Application of the semiconducting materials Springer Handbook of Condensed Matter and Materials Data Springer Handbook of Condensed Matter and Materials Data Generates high frequency laser without frequency doubling Frequency Doubling also known as "second harmonic generation"
using nonlinear optics mechanism to double the ennergy of source photon
an example is the green laser pointer http://upload.wikimedia.org/wikipedia/commons/5/5f/Green-laser-pointer-dpss-diagrams.jpg HAZARD: AlGaInP is toxic and is irritating to skin,eyes and lungs! AlGaInP is used in manufacturing of high brightness LED of
different color. It has direct band gap which make it a good light emitting material why? For a direct band gap material
,emiting light only involves
emission of a single photon. For a indirect band gap material
, emiting light involves emission
of a single photon and a abosption of a phonon(change k).
It is of much lower probability. Disc Popular Storage Device 3 types of Disc:
Compact Disc (CD)
Digital Video Disc (DVD)
Blu-ray Disc (BRD) Pits and Capacity of Storage smaller pits
= higher density
= larger capacity But we need smaller wavelength of laser to read smaller pits http://bluraydisc.com/en/about/WhatisBlurayDisc/BDvsDVD.html How does disc store information? Source light intensity detector http://euphrates.wpunj.edu/faculty/kerzner/CurrentFolder/SEAIVKeynote6.pdf Light coming from the laser diode is focused on the disc
intensity of reflected light depends on the surface structure
signal is processed to restore the original information GaAs is commonly used in solar cell and detector. band gap = 1.9~2.1eV Pioneer is developing an optical disc that holds 500 GB of data using ultaviolet instead of blue ray. a ~ 5.6A The End
Thank you! AlGaInP has wider band gap. It has a smaller focus spot and shorter wavelength.It allow smaller pits on the disc and hence greater amount of storage. Even further... The smallest pit (~900nm in CDs) When the pit passes by the laser spot Intensity detected Information Intepreted Intensity detected 3D optical storage device
Making use of the whole disc
to store information. Holography imaging
Real 3D image.. 1877: Thomas Edison, an American inventor and scientist, invented the phonograph.
1949: 7-inch 45 rpm records introduced in the US markets.
1960: Laser technology introduced by Theodore Maiman and used for data storage in CDs.
1965: James Russell, an American inventor, introduced the concept of optical digital recording and playback.
1978: Sony demonstrated an advanced version of optical digital audio disc with playing time of 150 minutes.
1982: First ever album on a CD released by Sony, which was Billy Joel’s 52nd Street.
1983: CD players and discs hit the market in the US and the rest of the world.
1984: Advanced technology to store and retrieve data from CD-ROM introduced.
1996: DVD technology hit the world, through the collaboration of leading computer companies such as Sun, Apple, Dell.
1997: DVD released in the market, sidelining CDs. Rewritable CDs and CD-RW introduced in the market.
2000: The DVR Blue prototypes are unveiled, later to become known as Blu-Ray discs.
2003: The first comsumer available Blue-Ray player is released in Japan by Sony.
(http://www.voices.com/articles/audio-recording-technology/cd-history-timeline.html) TimeLine of Disc Storage Band Structure Springer Handbook of Condensed Matter and Materials Data band gap = 3.4eV