icfm2001 crimia october 1-5, 2001 recent advances in magneto-optics katsuaki sato department of...

ICFM2001 Crimia October 1-5, 2001

Recent Advances in Magneto-Optics

Katsuaki SatoDepartment of Applied Physics

Tokyo University of Agriculture & Technology


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


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


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


2.1 Faraday Effect

• (a) Faraday Configuration: – Magnetization // Light Vector

• (b)Voigt Configuration:– Magnetization Light Vector


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 ）


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


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


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 ）


Magneto-optical Kerr effect

Polar Longitudinal Transverse

M M M


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


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


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~


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


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


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


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


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


Microscopic concepts of electronic polarization

= +++ + 　・・

+ + -

-

Unperturbed wavefunction

Wavefunction perturbed by electric field

E

S-like P-like

Expansion by unperturbed orbitals


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


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


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


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


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.


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


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


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


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


Electronic states and optical transitions of Co2+ and Co3+ in Y3Fe5O12

(a) (b)


Theoretical and experimental magneto-optical spectra of Co-doped Y3Fe5O12


Theoretical and experimental MO spectra of bcc Fe

Katayama

theory

Krinchik


(a) (b) (c)

MO spectra of PtMnSb

Magneto-opticalKerr rotation θK

and ellipticity ηKDiagonal dielectric functions

Off-diagonal Dielectric function

xxxx

xyK

1


Comparison of theoretical and experimental spec

traof half-metallic PtMnSb

(a)

(b)

(d)

(c)

After Oppeneer


Magneto-optical spectra of CdMnTe

Photon Energy (eV)

Far

aday

ro t

a tio

n s p

e ctr

a (d

eg)


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)


Wavelength (nm)P

ola

r K

err

ro

tatio

n (

min

)

MO spectra in RE-TM (1)


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


MO spectra of Fe/Au superlattice


Calculated MO spectra of Fe/Au superlattice

By M.Yamaguchi et al.


Au/Fe/Au sandwich structure

By Y.Suzuki et al.


4. Recent Advances in Magneto-Optics

• Nonlinear magneto-optics

• Scanning near-field magneto-optical microscope (MO-SNOM)

• X-ray magneto-optical Imaging


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


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


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


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°


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


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


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


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


Collection mode(a) and illumination mode(b)


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


topography MO image

Recorded marks on MO diskobserved by MO-SNOM


MO-SNOM image of 0.2m recorded marks on Pt/Co MO disk

MO image

Resolution ↓Resolution ↓

Line profileTopographicimage


Reflection type SNOM

P. Fumagalli, A. Rosenberger, G. Eggers, A. Münnemann, N. Held, G. Güntherodt: Appl. Phys. Lett. 72, 2803 (1998)


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)


(b)

Magnetic circular dichroism of L-edge


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.


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


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


5. Magneto-optical Application

• Magneto-optical disk for high density storage

• Optical isolators for optical communication

• Other applications


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


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)


Structure of MO disk media

• MO disk structurePolycarbonatesubstrate

SiNx layer for protection and MO-enhancement

MO-recording layer(amorphous TbFeCo)

Al reflectionlayer

LandGrooveResin


• 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


• 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


アモルファス TbFeCo 薄膜

TM(Fe,C

o)

TM(Fe,C

o)

R(Tb)

R(Tb)


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


Shape of Recorded Marks

(a) LIM

(b) MFM


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


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


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)


• 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


Illustration of 3 kinds of MSR


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)


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+


MAMMOSMAMMOS(magnetic amplification MO system)(magnetic amplification MO system)


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


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.


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


SIL (solid immersion lens)


Optical recording using SIL


Hybrid Recording

H. Saga et al. DigestMORIS/APDSC2000, TuE-05, p.92.

405nmLD

TbFeCodisk

ReadoutMR head

Recording head(SIL)

Achieved 60Gbit/in2


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


Optical circuit elements proposed by Dillon

(a) Rotator (b) Isolator

(c) Circulator

(d) Modulator(e) Latching switch


Optical isolator for Laser diode module

Optical isolator for LD module

Optical fiberSignal source

Laser diode module


Optical fiber amplifier and optical isolator

EDFAisolators

mixer

Pumping laser

Band pass filter

outputinput


Optical Circulator

A

B

C

D


Optical add-drop and circulator

circulatorFiber grating

circulator


Polarization dependent isolator

polarizer

analyzermag.field

Faradayrotator

input

reflected beam


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


Magneto-optical circulator

Prism polarizer A Faraday rotator

Prism polarizer B

Half wave plate

Port 1

Port 3

Port 2

Port 4

Reflection prism


Optical absorption in YIG


Waveguide type isolators


Mach-Zehnder type isolator


Current-field sensor


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


Field sensor using optical fibers


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.

icfm2001 crimia october 1-5, 2001 recent advances in magneto-optics katsuaki sato department of...

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