introduction to optoelectronics optical storage (1) prof. katsuaki sato
TRANSCRIPT
![Page 1: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/1.jpg)
Introduction to OptoelectronicsOptical storage (1)
Prof. Katsuaki Sato
![Page 2: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/2.jpg)
Let’s talk on optical storages!
• Can you tell difference between storages and memories?
• There are a lot of different information storage techniques. What sort of storage devices do you know?
• Can you tell the peculiarity of optical storages in these storages?
Point of discussionDensity, capacity, transfer rate, size, removability
![Page 3: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/3.jpg)
Storages• Old storage: stones, paper, films, photographs,
record• Advanced storage• Audio/Video use
– Analog: audio cassette, video tape– Digital: CD, MD, Digital video tape, DVD, HD
• Computer use– Magnetic: MT, FD, HD– Optical: CD-ROM, CD-R, CD-RW, MO, DVD-ROM, DVD-
R, DVD-RW– Semiconductor: Flash memory (USB memory)
![Page 4: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/4.jpg)
Old storages
• Woods, Bamboo• Stone: example Rosetta Stone• Paper: books, notebooks, etc.• Films: movies, photographs
![Page 5: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/5.jpg)
Magnetic Tape (MT)
• Tape recorder
![Page 6: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/6.jpg)
Magnetic recording
• History• Magnetic tape and magnetic disk• Recording media and recording head• GMR head for high density• Magneto-optical recording• Hybrid magnetic recording• Solid state nonvolatile magnetic memory
(MRAM)
![Page 7: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/7.jpg)
History of magnetic recording
• 1898 V. Poulsen (Denmark) invented wire recorder; Information storage technology by control of magnetic state.
• 1900 The magnetic recorder was exhibited at the Paris EXPO and was praised as “the most interesting invention of recent years”.
• Invention of vacuum tube amplifier by L. De Forest (USA) in1921, together with development of the ring-type magnetic head and the fine magnetic powder applied tape bring about practical magnetic recorder.
![Page 8: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/8.jpg)
Recording process
K. Sato ed., Applied Materials Science(Ohm publishing) Fig. 5.18
Recording currenttime
moving directionof recording media
Recorded wavelength
![Page 9: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/9.jpg)
Recording process
• Signal current is applied to a coil in the magnetic head which is placed close to the recording medium to generate the magnetic flux, the intensity and direction of which is proportional to the signal.
• The medium is magnetized by the magnetic flux from the head, leading to formation of magnetic domain corresponding to the intensity and polarity of the signal.
• Recorded wavelength ( the length of recorded domain corresponding to one period of the signal) is calculated by =v/f where v is the relative velocity between head and medium, and f the signal frequency)
![Page 10: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/10.jpg)
Read out of recorded signal ( 1 )Inductive head
• Electromagnetic inductionElectric voltage proportional to the derivative of the magnetic flux is generated
• Output has the differential form of the recorded signal
• The readout voltage is proportional to the product of the recorded wavelength and relative velocity between the head and the medium.
tE
Spacing loss
Principle of read-out
induction
K. Sato ed., Applied Materials Science(Ohm publishing) Fig. 5.19, 5.20
Running direction
![Page 11: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/11.jpg)
Read out of recorded signal ( 2 ) MR (magneto-resistance) head
• Change of the electric resistance of the head by the magnetic flux from the medium is utilized.
• AMR (anisotropic magneto-resistance) was utilized in the early stage and was replaced to GMR (giant magneto-resistance).
N S N SN S
leakage flux
MR head
N S
![Page 12: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/12.jpg)
Magnetization curve and GMR
• If F1 and F2 have different Hc then high resistivity state is realized for H between Hc1 and Hc2
H
M
R
H
F1
F2
F1
F2
HC2HC1
F1
F2
F1
F2
F1
F2
Resistance is high for anti-parllel configuration
![Page 13: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/13.jpg)
What is GMR?
• Ferromag(F 1 )/Nonmag(N)/Ferromag(F2) multilayer• Small resistance for parallel spin direction of F1 and
F2, while high resistance for antiparallel direction.
Pinned layer
Free layer
![Page 14: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/14.jpg)
Spin valve
• NiFe(free)/Cu/NiFe(pinned)/AF(FeMn) uncoupled sandwich structure
Exchange bias
Free layer
NonmagnetoclayerPinned layer
Antiferromagnetic ( 例 FeMn)
Synthetic antiferro
![Page 15: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/15.jpg)
Head clearance
![Page 16: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/16.jpg)
Increase of areal recorded density
Superparamagnetic limit
MR head
GMR head
![Page 17: Introduction to Optoelectronics Optical storage (1) Prof. Katsuaki Sato](https://reader033.vdocuments.site/reader033/viewer/2022061607/56649c7d5503460f9493245b/html5/thumbnails/17.jpg)
Limit of increase in density is coming
• Until 2000 the increase rate was 100 times per 10 years but it becomes slower.
• The reason of slowing is due to superparamagnetism due to smallness of the recorded region for one bit.
• By the use of perpendicular recording the drawback will be overcome.