Recent Advances in Magneto-Optics
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ICFM2001 Crimia October 1-5, 2001
Recent Advances in Magneto-Optics
Katsuaki SatoDepartment of Applied Physics
Tokyo University of Agriculture & Technology
ICFM2001 Crimia October 1-5, 2001
CONTENTS1. Introduction2. Fundamentals of Magneto-Optics3. Magneto-Optical Spectra
• Experiments and theory
4. Recent Advances in Magneto-Optics• Magneto-optics in nano-structures• Nonlinear magneto-optical effect• Scanning near-field magneto-optical microscope
5. Current Status in Magneto-Optical Devices• Magneto-optical disk storages• Magneto-optical isolators for optical communication• Other applications
6. Summary
ICFM2001 Crimia October 1-5, 2001
1. Introduction
• Magneto-Optical Effect : Discovered by Faraday on 1845
• Phenomenon : Change of Linear Polarization to Elliptically Polarized Light Accompanied by Rotation of Principal Axis
• Cause : Difference of Optical Response between LCP and RCP
• Application :– Magneto-Optical Disk
– Optical Isolator
– Current Sensors
– Observation Technique
ICFM2001 Crimia October 1-5, 2001
2.Fundamentals of Magneto-Optics
• MO Effect in Wide MeaningAny change of optical response induced by magnetizatio
n
• MO Effect in Narrow MeaningChange of intensity or polarization induced by magentizat
ion – Faraday effect– MOKE(Magneto-optical Kerr effect)– Cotton-Mouton effect
ICFM2001 Crimia October 1-5, 2001
2.1 Faraday Effect
• (a) Faraday Configuration: – Magnetization // Light Vector
• (b)Voigt Configuration:– Magnetization Light Vector
ICFM2001 Crimia October 1-5, 2001
Faraday Effect• MO effect for optical transmission
– Magnetic rotation ( Faraday rotation ) F
– Magnetic Circular Dichroism ( Faraday Ellipticity ) F
• Comparison to Natural Optical Rotation– Faraday Effect is Nonreciprocal (Double rotation for round tr
ip)
– Natural rotation is Reciprocal (Zero for round trip)
• Verdet Constant F=VlH (For paramagnetic and diamagnetic materials )
ICFM2001 Crimia October 1-5, 2001
Illustration of Faraday Effect
For linearly polarized light incidence,
• Elliptically polarized light goes out (MCD)
• With the principal axis rotated (Magnetic rotation)Linearly polarized
light
EllipticallyPolarized light
Rotation of Principal axis
ICFM2001 Crimia October 1-5, 2001
Faraday rotation of magnetic materialsMaterials rotation
(deg) figure of
merit(deg/dB)wavelength
(nm)
temperature(K)
Mag. field(T)
Fe 3.825 ・ 105 578 RT 2.4
Co 1.88 ・ 105 546 〃 2
Ni 1.3 ・ 105 826 120 K 0.27
Y3Fe5O12 250 1150 100 K
Gd2BiFe5O12 1.01 ・ 104 44 800 RT
MnSb 2.8 ・ 105 500 〃
MnBi 5.0 ・ 105 1.43 633 〃
YFeO3 4.9 ・ 103 633 〃
NdFeO3 4.72 ・ 104 633 〃
CrBr3 1.3 ・ 105 500 1.5K
EuO 5 ・ 105 104 660 4.2 K 2.08
CdCr2S4 3.8 ・ 103 35(80K) 1000 4K 0.6
ICFM2001 Crimia October 1-5, 2001
2.2 Magneto-Optical Kerr Effect
• Three kinds of MO Kerr effects– Polar Kerr ( Magnetization is oriented perpen
dicular to the suraface )– Longitudinal Kerr ( Magnetization is in plane
and is parallel to the plane of incidence )– Transverse Kerr ( Magnetization is in plane
and is perpendicular to the plane of incidence )
ICFM2001 Crimia October 1-5, 2001
Magneto-optical Kerr effect
Polar Longitudinal Transverse
M M M
ICFM2001 Crimia October 1-5, 2001
MO Kerr rotation of magnetic materialsMaterials rotation Photon
energytemperature field
(deg) (eV) (K) (T)
Fe 0.87 0.75 RT
Co 0.85 0.62 〃
Ni 0.19 3.1 〃
Gd 0.16 4.3 〃
Fe3O4 0.32 1 〃
MnBi 0.7 1.9 〃
PtMnSb 2.0 1.75 〃 1.7
CoS2 1.1 0.8 4.2 0.4
CrBr3 3.5 2.9 4.2
EuO 6 2.1 12
USb0.8Te0
.2
9.0 0.8 10 4.0
CoCr2S4 4.5 0.7 80
a-GdCo *
0.3 1.9 RT
CeSb 90 2
ICFM2001 Crimia October 1-5, 2001
2.3 Electromagnetism and Magnetooptics
• Light is the electromagnetic wave.• Transmission of EM wave : Maxwell equation• Medium is regareded as continuum→dielectric permeabi
lity tensor– Effect of Magnetic field→mainly to off-diagonal element
• Eigenequation• →Complex refractive index : two eigenvalues
eigenfunctions : right and left circularpolarization– Phase difference between RCP and LCP→rotation– Amplitude difference →circular dichroism
ICFM2001 Crimia October 1-5, 2001
Dielectric tensor
ED 0~ ε
zzzyzx
yzyyyx
xzxyxx~
ijijij
Isotromic media ; M//zInvariant C4 for 90°rotation around z-axis
zzzxzy
xzxxxy
yzyxyy
CC 41
4~~
0
zyzxyzxz
xyyx
yyxx
zz
xxxy
xyxx
00
0
0~
ICFM2001 Crimia October 1-5, 2001
MO Equations (1)
0~
2
2
2
Etc
Erotrot
0
00
0ˆ0ˆ
2
2
z
y
x
zz
xxxy
xyxx
E
E
E
N
N
xyxx iN 2ˆEigenvalue
Eigenfunction : LCP and RCP
Without off-diagonal terms : No difference between LCP & RCP
No magnetooptical effect
Maxwell Equation
Eigenequation
ICFM2001 Crimia October 1-5, 2001
MO Equations (2)
xx
yxyxxxyxxx iiiNNN
ˆˆˆ
2)2(21)0(
)1(
ˆ
M
Mi
iN
xxxx
xy
xx
yxF
Both diagonal and off-diagonal terms contribute toMagneto-optical effect
ICFM2001 Crimia October 1-5, 2001
Phenomenology of MO effectLinearly polarized light can be decomposed to LCP and RCP
Difference in phase causes rotation ofthe direction of Linear polarization
Difference in amplitudes makes Elliptically polarized light
In general, elliptically polarized lightWith the principal axis rotated
ICFM2001 Crimia October 1-5, 2001
2.4 Electronic theory of Magneto-Optics
• Magnetization→Splitting of spin-states– No direct cause of difference of optical response
between LCP and RCP
• Spin-orbit interaction→Splitting of orbital states– Absorption of circular polarization→Induction of circular
motion of electrons
• Condition for large magneto-optical response– Presence of strong (allowed) transitions– Involving elements with large spin-orbit interaction– Not directly related with Magnetization
ICFM2001 Crimia October 1-5, 2001
Dielectric functions derived from Kubo formula
22
0
2
20
20
2
2
1
mn
mnmn
nmnxy
n n
mnxmnxx
i
f
m
Nqi
i
f
m
Nq
nn
nnn kT
kT
kTH
kT
)/exp(
)/exp(
)/exp(Tr
)/exp(
0
where
2
0 0 jxmf
jjo
mnmnmn fff
2
0 02 xjmf jxj
ICFM2001 Crimia October 1-5, 2001
Microscopic concepts of electronic polarization
= +++ + ・・
+ + -
-
Unperturbed wavefunction
Wavefunction perturbed by electric field
E
S-like P-like
Expansion by unperturbed orbitals
ICFM2001 Crimia October 1-5, 2001
Orbital angular momentum-selection rules and circular dichroism
Lz=0
Lz=+1
Lz=-1
s-like
p-=px-ipy
p+=px+ipy
px-orbitalpy-orbital
ICFM2001 Crimia October 1-5, 2001
Role of Spin-Orbit Interaction
L=1
L=0
LZ=+1,0,-1
LZ=0
Jz=-3/2Jz=-1/2
Jz=+1/2Jz=+3/2
Jz=-1/2
Jz=+1/2
Exchange splitting
Exchange
+spin-orbit
Without magnetization
ICFM2001 Crimia October 1-5, 2001
MO lineshapes (1)
Excited state
Ground state
0 1 2
Without magnetization
With magnetization
Lz=0
Lz=+1
Lz=-1
1+2
Photon energy Photon energy
’xy ”xy
1.Diamagnetic lineshape
ICFM2001 Crimia October 1-5, 2001
MO lineshapes (2)
excited state
ground state
f+ f-
f=f+ - f-
0
without magneticfield
with magneticfield
’xy
”xy
photon energy
(a) (b)d
iele
ctri
c co
nst
ant
2.Paramagnetic lineshape
ICFM2001 Crimia October 1-5, 2001
3. Magneto-Optical Spectra
• Measurement technique• Magnetic garnets• Metallic ferromagnet : Fe, Co, Ni• Intermetallic compounds and alloys : PtMnSb et
c.• Magnetic semiconductor : CdMnTe etc.• Superlattices : Pt/Co, Fe/Au etc.• Amorphous : TbFeCo, GdFeCo etc.
ICFM2001 Crimia October 1-5, 2001
Measurement of magneto-optical spectra using retardation modulation technique
i
j
/4
P
PEM A
D
quartz Isotropicmedium
B
fused silica CaF2
Ge etc.
Piezoelectriccrystal
amplitude
position
l
Retardation=(2/)nl sin pt =0sin pt
sample
eletromagnetpolarizer
analyzerdetector
sample
computer
monochromator
ellipsoidal mirror
chopperfilterLight source
ICFM2001 Crimia October 1-5, 2001
Magnetic garnets
• One of the most intensively investigated magneto-optical materials
• Three different cation sites; octahedral, tetrahedral and dodecahedral sites
• Ferrimagnetic• Large magneto-optical effect due to strong charge
-transfer transition• Enhancement of magneto-optical effect by Bi-sub
stitution at the dodecahedral site
ICFM2001 Crimia October 1-5, 2001
6S (6A1, 6A1g)
6P (6T2, 6T1g)
without perturbation
spin-orbit interaction
tetrahedral crystal field
(Td)
octahedral crystal field
(Oh)
J=7/2
J=5/2
J=3/2
5/2
-3/2
-
Jz=
3/27/2
3/2
3/2
5/2 -5/2
-3/2
-3/2
-3/2-7/2
Jz=
P+ P-P+ P-
Electronic level diagram of Fe3+ in magnetic garnets
ICFM2001 Crimia October 1-5, 2001
experiment
calculation
300 400 500 600
Wavelength (nm)
Far
aday
rot
atio
n (
arb
. un
it)
0
-2
0
+2
Far
aday
rot
atio
n
(deg
/cm
)
0.4
x104
0.8
-0.4
Experimental and calculated magneto-optical spectra of Y3Fe5O12
ICFM2001 Crimia October 1-5, 2001
Electronic states and optical transitions of Co2+ and Co3+ in Y3Fe5O12
(a) (b)
ICFM2001 Crimia October 1-5, 2001
Theoretical and experimental magneto-optical spectra of Co-doped Y3Fe5O12
ICFM2001 Crimia October 1-5, 2001
Theoretical and experimental MO spectra of bcc Fe
Katayama
theory
Krinchik
ICFM2001 Crimia October 1-5, 2001
(a) (b) (c)
MO spectra of PtMnSb
Magneto-opticalKerr rotation θK
and ellipticity ηKDiagonal dielectric functions
Off-diagonal Dielectric function
xxxx
xyK
1
ICFM2001 Crimia October 1-5, 2001
Comparison of theoretical and experimental spec
traof half-metallic PtMnSb
(a)
(b)
(d)
(c)
After Oppeneer
ICFM2001 Crimia October 1-5, 2001
Magneto-optical spectra of CdMnTe
Photon Energy (eV)
Far
aday
ro t
a tio
n s p
e ctr
a (d
eg)
ICFM2001 Crimia October 1-5, 2001
Pt/Co superlattices
Photon energy (eV)
Photon energy (eV)
simulationexperiment
Ker
r ro
tatio
n an
d el
liptic
ity(m
in)
Ker
r ro
tatio
n an
d el
liptic
ity(m
in)
rotation
elliptoicity
PtCo alloy
Pt(10)/Co(5) Pt(18)/Co(5)
Pt(40)/Co(20)
ICFM2001 Crimia October 1-5, 2001
Wavelength (nm)P
ola
r K
err
ro
tatio
n (
min
)
MO spectra in RE-TM (1)
ICFM2001 Crimia October 1-5, 2001
5 4 3 2
Photon Energy (eV)
0
-0.2
-0.4
-0.6
Pol
ar K
err
rota
tion
(deg
)
Wavelength (nm)
300 400 500 600 700
MO spectra in R-Co
ICFM2001 Crimia October 1-5, 2001
MO spectra of Fe/Au superlattice
ICFM2001 Crimia October 1-5, 2001
Calculated MO spectra of Fe/Au superlattice
By M.Yamaguchi et al.
ICFM2001 Crimia October 1-5, 2001
Au/Fe/Au sandwich structure
By Y.Suzuki et al.
ICFM2001 Crimia October 1-5, 2001
4. Recent Advances in Magneto-Optics
• Nonlinear magneto-optics
• Scanning near-field magneto-optical microscope (MO-SNOM)
• X-ray magneto-optical Imaging
ICFM2001 Crimia October 1-5, 2001
NOMOKE( Nonlinear magneto-optical Kerr
effect )• Why SHG is sensitive to surfaces?
• Large nonlinear magneto-optical effect
• Experimental results on Fe/Au superlattice
• Theoretical analysis
• Future perspective
ICFM2001 Crimia October 1-5, 2001
LD pump SHG laser
lens
Mirror
Chopper
Lens
Analyzer
Filter
PMT
Ti: sapphirelaser
Mirror
Filter
polarizer
Berek compensator
Sample
Stage controller
Electromagnet
Photon counter Computer
=532nm
=810nmPulse=150fsP=600mWrep80MHz
Photon counting
MSHG Measurement System
ICFM2001 Crimia October 1-5, 2001
P-polarized or S-polarized light
nm)
nm)
AnalyzerFilter
nm)
Pole piece
Rotatinganalyzer
試料回転
Sample stage
45°
Sample
Optical arrangements
ICFM2001 Crimia October 1-5, 2001[Fe(3.75ML)/Au(3.75ML)] 超格子の ( Pin Pout )配置の線形および非線形の方位角依存性
(a) Linear (810nm) (b) SHG (405nm)
・ Linear optical response (=810nm) The isotropic response for the azimuthal angle・ Nonlinear optical response (=405nm) The 4-fold symmetry pattern Azimuthal pattern show 45-rotation by reversing the magnetic field
050
100150200250300
0
30
6090
120
150
180
210
240270
300
330
050
100150200250300
020406080
100
0
30
6090
120
150
180
210
240270
300
330
020406080
100
SH
G in
ten
sity
(co
un
ts/1
0se
c.)
SH
G in
ten
sity
(co
un
ts/1
0se
c.)
45linear MSHG
Azimuthal dependence of
ICFM2001 Crimia October 1-5, 2001ASP=460, B=26, C=-88
(c) Sin-Pout
103
SH
G in
tens
ity
(cou
nts/
10se
c.)
ASS=100, B=26, C=-88
(d) Sin-Sout
103
APP=1310, B=26, C=-88
(a) Pin-Pout
103
SH
G in
tens
ity
(cou
nts/
10se
c.)
APS=-300, B=26, C=-88
(b) Pin-Sout
103
Dots : exp.Solid curve :calc.
Calculated and experimental patterns :x=3.5
ICFM2001 Crimia October 1-5, 2001
Fe(1.75ML)/Au(1.75ML) Sin
The curves show a shift for two opposite directions of magnetic field
S-polarized lightω(810nm)
2 (405nm)
Analyzer
45°
Electromagnet
Rotating Analyzer
Filter
Nonlinear Kerr Effect
= 31.1°
ICFM2001 Crimia October 1-5, 2001
Nonlinear Magneto-optical Microscope
Schematic diagram
LP F1
Objective lens
Sample
F2
A
CCD Linear and nonlinear magneto-optical images of domains in CoNi film
50m
ICFM2001 Crimia October 1-5, 2001
MO-SNOM(Scanning near-field magneto-optical
microscope)
• Near-field optics
• Optical fiber probe
• Optical retardation modulation technique
• Stokes parameter of fiber probe
• Observation of recorded bits on MO disk
ICFM2001 Crimia October 1-5, 2001
Near-field
Critical anglec
Medium 2
Medium 1
ic
ic
Evanescent wave
Total reflection and near field
d
Propagating wave
Evanescent field
Scattered wave
Scattered wave by a small sphere placed in the evanescent field produced by another sphere
ICFM2001 Crimia October 1-5, 2001
Levitation control methods
Sample surface
Fiber probe
Quartz oscillator
Piezoelectrically-driven xyz-stage
Piezoelectrically-driven xyz-stage
bimorph
LDPhoto diode
Shear force type Canti-lever type
ICFM2001 Crimia October 1-5, 2001
Collection mode(a) and illumination mode(b)
ICFM2001 Crimia October 1-5, 2001
SNOM/AFM System
Bent fiber probe Controller(SPI3800 3800)
PEM Ar ionlaser
Signal
generatorLock-inAmplifier
Computer
XYZ
scanner
Bimorph
Filter
Sample
Photodiode
Photomultiplier
Optical fiber probe
Analyzer
Polarizer
CompensatorLD
MO-SNOM system using PEM
ICFM2001 Crimia October 1-5, 2001
topography MO image
Recorded marks on MO diskobserved by MO-SNOM
ICFM2001 Crimia October 1-5, 2001
MO-SNOM image of 0.2m recorded marks on Pt/Co MO disk
MO image
Resolution ↓Resolution ↓
Line profileTopographicimage
ICFM2001 Crimia October 1-5, 2001
Reflection type SNOM
P. Fumagalli, A. Rosenberger, G. Eggers, A. Münnemann, N. Held, G. Güntherodt: Appl. Phys. Lett. 72, 2803 (1998)
ICFM2001 Crimia October 1-5, 2001
2p1/2
2p3/2
3d
(12)
(6)
(2)
(1)
(3)
(6) (6)
(3)
(3)
(14)
(a)
(b)
+1/2 -1/2
+3/2 +1/2 -1/2 -3/2mj
mj
+2 +1 0 -1 -2md
Occupation of minority 3d band
X MCD (X-ray magnetic circular dichroism)
Simulated XMCD spectra corresponding to transitions (a) and (b) in the left diagram
(a) (b)
ICFM2001 Crimia October 1-5, 2001
(b)
Magnetic circular dichroism of L-edge
ICFM2001 Crimia October 1-5, 2001
Domain image of MO media observed using XMCD of Fe L3-edge
SiN(70nm)/ TbFeCo(50nm)/SiN(20nm)/Al(30nm)/SiN(20nm) MO 媒体
N. Takagi, H. Ishida, A. Yamaguchi, H. Noguchi, M. Kume, S. Tsunashima, M. Kumazawa, and P. Fischer: Digest Joint MORIS/APDSC2000, Nagoya, October 30-November 2, 2000, WeG-05, p.114.
ICFM2001 Crimia October 1-5, 2001
Spin dynamics in nanoscale region
Th. Gerrits, H. van den Berg, O. Gielkens, K.J. Veenstra and Th. Rasing: Digest Joint MORIS/APDSC2000, Nagoya, October 30-November 2, 2000, TuC-05, p.24.
GaAs high speed optical switch
ICFM2001 Crimia October 1-5, 2001
Further Prospects- For wider range of researches -
• Time (t) : Ultra-short pulse→Spectroscopy using ps, fs-lasers, Pump-probe technique
• Frequency () : Broad band width, Synchrotron radiation
• Wavevector (k) : Diffraction, scattering, magneto-optical diffraction
• Length (x) : Observation of nanoscale magetism, Appertureless SNOM, Spin-polarized STM, Xray microscope
• Phase () : Sagnac interferrometer
ICFM2001 Crimia October 1-5, 2001
5. Magneto-optical Application
• Magneto-optical disk for high density storage
• Optical isolators for optical communication
• Other applications
ICFM2001 Crimia October 1-5, 2001
Magneto-optical (MO) Recording• Recording:Thermomagnetic recordingRecording:Thermomagnetic recording
– Magnetic recording using laser irradiationMagnetic recording using laser irradiation
• Reading out: Magneto-optical effectReading out: Magneto-optical effect– Magnetically induced polarization state
• MO disk, MD(Minidisk)
• High rewritability : more than 107 times
• Complex polarization optics
• New magnetic concepts: MSR, MAMMOS
ICFM2001 Crimia October 1-5, 2001
History of MO recording• 1962 Conger,Tomlinson Proposal for MO memory• 1967 Mee Fan Proposal of beam-addressable MO recording• 1971 Argard (Honeywel) MO disk using MnBi films• 1972 Suits(IBM) MO disk using EuO films• 1973 Chaudhari(IBM) Compensation point recording to a-GdCo film• 1976 Sakurai(Osaka U) Curie point recording on a-TbFe films1980 Imamura
(KDD) Code-file MO memory using a-TbFe films• 1981 Togami(NHK) TV picture recording using a-GdCo MO disk• 1988 Commercial appearance of 5”MO disk (650MB)• 1889 Commercial appearance of 3.5 ”MO disk(128MB)• 1991 Aratani(Sony) MSR• 1992 Sony MD• 1997 Sanyo ASMO(5” 6GB : L/G, MFM/MSR) standard• 1998 Fujitsu GIGAMO(3.5” 1.3GB)• 2000 Sanyo, Maxell iD-Photo(5cmφ730MB)
ICFM2001 Crimia October 1-5, 2001
Structure of MO disk media
• MO disk structurePolycarbonatesubstrate
SiNx layer for protection and MO-enhancement
MO-recording layer(amorphous TbFeCo)
Al reflectionlayer
LandGrooveResin
ICFM2001 Crimia October 1-5, 2001
• Temperature increase by focused laser beam
• Magnetization is reduced when T exceeds Tc
• Record bits by external field when cooling
MO recording How to record(1)
External field MO media
Temp
Laserspot
Tc
Coil
M
Tc
ICFM2001 Crimia October 1-5, 2001
• Use of compensation point
writing
• Amorphous TbFeCo:
Ferrimagnet with Tcomp
• HC takes maximum at Tcomp
– Stability of small recorded marks
MO recording How to record(2)
T
M TbFeCo
Tcomp
Hc
Mtotal
RTTcTbFe,Co
ICFM2001 Crimia October 1-5, 2001
アモルファス TbFeCo 薄膜
TM(Fe,C
o)
TM(Fe,C
o)
R(Tb)
R(Tb)
ICFM2001 Crimia October 1-5, 2001
Two recording modesTwo recording modes• Light intensity modulation
(LIM) : present MO– Laser light is modulated by
electrical signal– Constant magnetic field– Elliptical marks
• Magnetic field modulation (MFM) : MD, ASMO– Field modulation by electrical
signal– Constant laser intensity– Crescent-shaped marks
Modulatedlaser beam
Constantlaser beam
Constant fieldModulated field Magnetic head
(a) LIM (b) MFM
ICFM2001 Crimia October 1-5, 2001
Shape of Recorded Marks
(a) LIM
(b) MFM
ICFM2001 Crimia October 1-5, 2001
MO recording How to read
• Magneto-optical conversion of magnetic signal to electric signal
D1
D2
+
-LD
PolarizedBeamSplitter
S
N
N
S
N
S
Differentialdetection
ICFM2001 Crimia October 1-5, 2001
Structure of MO Head
Laser diode
Photo-detector
Focusing lens
Half wave-plate
lens
Beam splitter
PBS(polarizing beam splitter)
Rotation ofpolarization
Recorded marks
Track pitch
Bias field coil
MO film
mirror
ICFM2001 Crimia October 1-5, 2001
Advances in MO recordingAdvances in MO recording
1. Super resolution1. MSR
2. MAMMOS/DWDD
2. Use of Blue Lasers
3. Near field1. SIL
2. Super-RENS (AgOx)
ICFM2001 Crimia October 1-5, 2001
• Resolution is determined by diffraction limit
– d=0.6λ/NA, where NA=n sin α– Marks smaller than wavelength cannot
be resolved
• Separation of recording and reading layers
• Light intensity distribution is utilized
– Magnetization is transferred only at the heated region
MSR(Magnetically induced super-resolution)
α
d
ICFM2001 Crimia October 1-5, 2001
Illustration of 3 kinds of MSR
ICFM2001 Crimia October 1-5, 2001
AS-MO standard
LD wavelength 650 nmNA 0.6
Disk diameter 120 mmThickness 0.6 mmTrack pitch 0.6 μ m Land/Groove
Recording method MO & CAD-MSRModulation Laser pumped MFM
Signal processing PRMLbit density 0.235μ m) PR(1,1) or PR(1,2,1)
Velocity control ZCAV/ZCLVCode NRZI+ (DC supressed)
ICFM2001 Crimia October 1-5, 2001
iD-Photo specification
Memory Capacity 730 MB
Surface memory density 4.6Gbit/in2 LD wavelength 650 nm
NA 0.6 Disk diameter 50.8 mm
Thickness 0.6 mm Track pitch 0.6 μ m Land/Groove
Recording method MO & CAD-MSR Modulation Pulsed laser strobe MFM bit density 0.235μ m
Signal processing, PRML PR(1,1) +Viterbi
Velocity control ZCAV Code NRZI+
ICFM2001 Crimia October 1-5, 2001
MAMMOSMAMMOS(magnetic amplification MO system)(magnetic amplification MO system)
ICFM2001 Crimia October 1-5, 2001
Super-RENSsuper-resolution near-field system
• AgOx film : decomposition and precipitation of Ag– Scattering center→near field
– Ag plasmon→enhancement
– reversible
• Applicable to both phase-change and MO recording 高温スポット
近接場散乱
ICFM2001 Crimia October 1-5, 2001
To shorter wavelengths
• DVD-ROM: Using 405nm laser, successful play back of marks was attained with track pitch =0.26m 、 mark length =213m (capacity 25GB) using NA=0.85 lens [i]。 [i] M. Katsumura, et al.: Digest ISOM2000, Sept. 5-9, 2000, Chitose, p. 18.
• DVD-RW: Using 405nm laser, read / write of recorded marks of track pitch=0.34m and mark length=0.29m in 35m two-layered disk(capacity:27GB) was succeeded using NA=0.65 lens, achieving 33Mbps transfer rate [ii] 。[ii] T. Akiyama, M. Uno, H. Kitaura, K. Narumi, K. Nishiuchi and N. Yamada: Digest ISOM2000, Sept. 5-9, 2000, Chitose, p. 116.
ICFM2001 Crimia October 1-5, 2001
Read/Write using Blue-violet LD and SIL (solid immersion lens)
405nm LD
SIL head
NA=1.5405nm80nm mark40GB
I. Ichimura et. al. (Sony), ISOM2000FrM01
ICFM2001 Crimia October 1-5, 2001
SIL (solid immersion lens)
ICFM2001 Crimia October 1-5, 2001
Optical recording using SIL
ICFM2001 Crimia October 1-5, 2001
Hybrid Recording
H. Saga et al. DigestMORIS/APDSC2000, TuE-05, p.92.
405nmLD
TbFeCodisk
ReadoutMR head
Recording head(SIL)
Achieved 60Gbit/in2
ICFM2001 Crimia October 1-5, 2001
Optical elements for fiber communication
• Necessity of optical isolators• Principles of optical isolators• Structure of optical isolators
– Polarization-independent type– Polarization-dependent type
• Optical multiplexing and needs of optical isolators
ICFM2001 Crimia October 1-5, 2001
Optical circuit elements proposed by Dillon
(a) Rotator (b) Isolator
(c) Circulator
(d) Modulator(e) Latching switch
ICFM2001 Crimia October 1-5, 2001
Optical isolator for Laser diode module
Optical isolator for LD module
Optical fiberSignal source
Laser diode module
ICFM2001 Crimia October 1-5, 2001
Optical fiber amplifier and optical isolator
EDFAisolators
mixer
Pumping laser
Band pass filter
outputinput
ICFM2001 Crimia October 1-5, 2001
Optical Circulator
A
B
C
D
ICFM2001 Crimia October 1-5, 2001
Optical add-drop and circulator
circulatorFiber grating
circulator
ICFM2001 Crimia October 1-5, 2001
Polarization dependent isolator
polarizer
analyzermag.field
Faradayrotator
input
reflected beam
ICFM2001 Crimia October 1-5, 2001
Polarization independent isolator
Fiber 2
Fiber 1
Forward direction
Reverse direction
½ waveplate C
Birefringent plate B2
B2B1 F C
Birefringent plate B1
Fiber 2
×
Faraday rotator F
×Fiber 1
ICFM2001 Crimia October 1-5, 2001
Magneto-optical circulator
Prism polarizer A Faraday rotator
Prism polarizer B
Half wave plate
Port 1
Port 3
Port 2
Port 4
Reflection prism
ICFM2001 Crimia October 1-5, 2001
Optical absorption in YIG
ICFM2001 Crimia October 1-5, 2001
Waveguide type isolators
ICFM2001 Crimia October 1-5, 2001
Mach-Zehnder type isolator
ICFM2001 Crimia October 1-5, 2001
Current-field sensor
ICFM2001 Crimia October 1-5, 2001
Current sensors used by power engineers
Before installation After installationMagnetic core
Hook
Magneto-optical sensor head
Fastening screw
Optical fiber
Fail-safe string
Aerial wire
ICFM2001 Crimia October 1-5, 2001
Field sensor using optical fibers
ICFM2001 Crimia October 1-5, 2001
SUMMARY
• Basic concepts of magneto-optics are described.
• Macroscopic and microscopic origins of magneto-optics are described.
• Some of the recent development of magneto-optics are also given.
• Some of the recent application are summarized.
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