Recent Advances in Magneto-Optics Katsuaki Sato Department of Applied Physics Tokyo University of Agriculture & Technology ICFM2001 Crimia October 1-5, 2001

CONTENTS Introduction Fundamentals of Magneto-Optics Magneto-Optical Spectra Experiments and theory Recent Advances in Magneto-Optics Magneto-optics in nano-structures Nonlinear magneto-optical effect Scanning near-field magneto-optical microscope Current Status in Magneto-Optical Devices Magneto-optical disk storages Magneto-optical isolators for optical communication Other applications 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 Meaning Any change of optical response induced by magnetization MO Effect in Narrow Meaning Change of intensity or polarization induced by magentization Faraday effect MOKE(Magneto-optical Kerr effect) Cotton-Mouton effect ICFM2001 Crimia October 1-5, 2001

2.1 Faraday Effect (a) Faraday Configuration: (b)Voigt 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 trip) 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 Rotation of Principal axis For linearly polarized light incidence, 　Elliptically polarized light goes out (MCD) With the principal axis rotated (Magnetic rotation) Elliptically Polarized light Linearly polarized light ICFM2001 Crimia October 1-5, 2001

Faraday rotation of magnetic materials (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 MnSb 2.8･105 500 MnBi 5.0･105 1.43 633 YFeO3 4.9･103 NdFeO3 4.72･104 CrBr3 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 perpendicular 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 ICFM2001 Crimia October 1-5, 2001

MO Kerr rotation of magnetic materials Photon energy temperature 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 EuO 6 2.1 12 USb0.8Te0.2 9.0 10 4.0 CoCr2S4 4.5 80 a-GdCo * 0.3 CeSb 90 2 ICFM2001 Crimia October 1-5, 2001 * "a-" means "amorphous".

2.3 Electromagnetism and Magnetooptics Light is the electromagnetic wave. Transmission of EM wave：Maxwell equation Medium is regareded as continuum→dielectric permeability 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 Isotromic media；M//z Invariant C4 for 90°rotation around z-axis ICFM2001 Crimia October 1-5, 2001

MO Equations (1) Maxwell Equation Eigenequation Eigenvalue Eigenfunction：LCP and RCP Without off-diagonal terms：No difference between LCP & RCP No magnetooptical effect ICFM2001 Crimia October 1-5, 2001

MO Equations (2) Both diagonal and off-diagonal terms contribute to Magneto-optical effect ICFM2001 Crimia October 1-5, 2001

Phenomenology of MO effect Linearly polarized light can be decomposed to LCP and RCP Difference in phase causes rotation of the direction of Linear polarization Difference in amplitudes makes Elliptically polarized light In general, elliptically polarized light With 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 where 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 py-orbital px-orbital p+=px+ipy Lz=+1 Lz=-1 p-=px-ipy Lz=0 s-like ICFM2001 Crimia October 1-5, 2001

Role of Spin-Orbit Interaction Jz=-3/2 Jz=-1/2 L=1 Jz=+1/2 LZ=+1,0,-1 Jz=+3/2 Jz=-1/2 L=0 Jz=+1/2 LZ=0 Exchange +spin-orbit Without magnetization Exchange splitting ICFM2001 Crimia October 1-5, 2001

MO lineshapes (1) 1.Diamagnetic lineshape Excited state Ground state 0 1 2  Without magnetization With Lz=0 Lz=+1 Lz=-1 1+2 Photon energy ’xy ”xy 1.Diamagnetic lineshape ICFM2001 Crimia October 1-5, 2001

MO lineshapes (2) 2.Paramagnetic lineshape excited state ground state f+ f-  f=f+ - f- 0 without magnetic field with magnetic ’xy ”xy photon energy (a) (b) dielectric constant ICFM2001 Crimia October 1-5, 2001

3. Magneto-Optical Spectra Measurement technique Magnetic garnets Metallic ferromagnet：Fe, Co, Ni Intermetallic compounds and alloys：PtMnSb etc. 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 j /4 P PEM A D quartz Isotropic medium B fused silica CaF2 Ge etc. Piezoelectric crystal amplitude position l Retardation =(2/)nl sin pt =0sin pt Light source chopper filter ellipsoidal mirror monochromator polarizer eletromagnet sample sample analyzer detector computer 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-substitution at the dodecahedral site ICFM2001 Crimia October 1-5, 2001

Electronic level diagram of Fe3+ in magnetic garnets 6S (6A1, 6A1g) 6P (6T2, 6T1g) without perturbation spin-orbit interaction tetrahedral crystal field (Td) octahedral (Oh) J=7/2 J=5/2 J=3/2 5/2 -3/2 - Jz= 3/2 7/2 5/2 -5/2 -3/2 -7/2 P+ P- ICFM2001 Crimia October 1-5, 2001

Experimental and calculated magneto-optical spectra of Y3Fe5O12 calculation 300 400 500 600 Wavelength (nm) Faraday rotation (arb. unit) -2 +2 Faraday rotation (deg/cm) 0.4 x104 0.8 -0.4 ICFM2001 Crimia October 1-5, 2001

Electronic states and optical transitions of Co2+ and Co3+ in Y3Fe5O12 (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 Krinchik theory ICFM2001 Crimia October 1-5, 2001

MO spectra of PtMnSb Magneto-optical Kerr rotation θK and ellipticity ηK Diagonal dielectric functions Off-diagonal Dielectric function (a) (b) (c) ICFM2001 Crimia October 1-5, 2001

(a) (b) (d) (c) Comparison of theoretical and experimental spectra of half-metallic PtMnSb After Oppeneer ICFM2001 Crimia October 1-5, 2001

Magneto-optical spectra of CdMnTe Photon Energy (eV) Faraday rotation spectra (deg) ICFM2001 Crimia October 1-5, 2001

Pt/Co superlattices simulation experiment Photon energy (eV) Kerr rotation and ellipticity(min) rotation elliptoicity PtCo alloy Pt(10)/Co(5) Pt(18)/Co(5) Pt(40)/Co(20) ICFM2001 Crimia October 1-5, 2001

MO spectra in RE-TM (1) ICFM2001 Crimia October 1-5, 2001 Wavelength (nm) Polar Kerr rotation (min) ICFM2001 Crimia October 1-5, 2001

MO spectra in R-Co Polar Kerr rotation (deg) Photon Energy (eV) -0.2 5 4 3 2 Photon Energy (eV) -0.2 -0.4 -0.6 Polar Kerr rotation (deg) Wavelength (nm) 300 400 500 600 700 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

MSHG Measurement System LD pump SHG laser lens Mirror Chopper Lens Analyzer Filter PMT Ti: sapphire laser polarizer Berek compensator Sample Stage　controller Electromagnet Photon counter Computer l=532nm l=810nm Pulse=150fs P=600mW rep80MHz Photon counting ICFM2001 Crimia October 1-5, 2001

P-polarized or S-polarized light Sample 試料回転 Sample stage w (810nm) Pole piece P-polarized or S-polarized light 45° Rotating analyzer w (810nm) Filter Analyzer Optical arrangements 2w (405nm) ICFM2001 Crimia October 1-5, 2001

Azimuthal dependence of ・　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 MSHG linear 45 SHG intensity (counts/10sec.) SHG intensity (counts/10sec.) (a)　Linear (810nm) (b)　SHG (405nm) [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 ICFM2001 Crimia October 1-5, 2001

Calculated and experimental patterns :x=3.5 Dots：exp. Solid curve：calc. APP=1310, B=26, C=-88 (a) Pin-Pout 103 SHG intensity (counts/10sec.) APS=-300, B=26, C=-88 (b) Pin-Sout 103 ASP=460, B=26, C=-88 (c) Sin-Pout 103 SHG intensity (counts/10sec.) ASS=100, B=26, C=-88 (d) Sin-Sout 103 ICFM2001 Crimia October 1-5, 2001

Nonlinear Kerr Effect S-polarized light ω(810nm) 2w (405nm) Analyzer 45° Electromagnet Rotating Filter Df = 31.1° The curves show a shift for two opposite directions of magnetic field Fe(1.75ML)/Au(1.75ML)　Sin ICFM2001 Crimia October 1-5, 2001

Nonlinear Magneto-optical Microscope Linear and nonlinear magneto-optical images of domains in CoNi film 50m Schematic diagram L P F1 Objective lens Sample F2 A CCD 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 Medium 1 Evanescent wave ic Medium 2 Critical angle c Propagating wave Evanescent field Scattered wave Critical angle c Medium 2 Medium 1 ic ic Evanescent wave Total reflection and near field 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 LD Photo 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

MO-SNOM system using PEM SNOM/AFM System Controller (SPI3800 3800) PEM Ar ion laser Signal generator Lock-in Amplifier Computer XYZ scanner Bimorph Filter Sample Photodiode Photomultiplier Optical fiber probe Analyzer Polarizer Compensator LD MO-SNOM system using PEM Bent fiber probe ICFM2001 Crimia October 1-5, 2001

Recorded marks on MO disk observed by MO-SNOM topography MO image ICFM2001 Crimia October 1-5, 2001

MO-SNOM image of 0.2m recorded marks on Pt/Co MO disk Resolution ↓ Topographic image MO image Line profile 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

ＸMCD (X-ray magnetic circular dichroism) 2p1/2 2p3/2 3d (12) (6) (2) (1) (3) (14) (a) (b) +1/2 -1/2 +3/2 -3/2 mj +2 +1 -1 -2 md Occupation of minority 3d band Simulated XMCD spectra corresponding to transitions (a) and (b) in the left diagram (a) (b) ICFM2001 Crimia October 1-5, 2001

Magnetic circular dichroism of L-edge (b) 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 GaAs high speed optical switch 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. 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 recording Magnetic recording using laser irradiation Reading 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 structure Polycarbonate substrate SiNx layer for protection and MO-enhancement Al reflection layer MO-recording layer (amorphous TbFeCo) Groove Land Resin ICFM2001 Crimia October 1-5, 2001

MO recording How to record(1) Temperature increase by focused laser beam Magnetization is reduced when T exceeds Tc Record bits by external field when cooling M Tc Temp Tc Laser spot MO media Coil External field ICFM2001 Crimia October 1-5, 2001

MO recording How to record(2) Use of compensation point writing Amorphous TbFeCo: Ferrimagnet with Tcomp HC takes maximum at Tcomp Stability of small recorded marks Hc M Tb FeCo Mtotal Fe,Co Tb Tcomp Tc T RT ICFM2001 Crimia October 1-5, 2001

アモルファスTbFeCo薄膜 TM (Fe,Co) R (Tb) ICFM2001 Crimia October 1-5, 2001

Two 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 Modulated laser beam Constant Constant field Modulated 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 + - LD D2 Differential detection Polarized Beam Splitter N S S N N S ICFM2001 Crimia October 1-5, 2001

Structure of MO Head ICFM2001 Crimia October 1-5, 2001 Bias field coil Laser diode Photo-detector Focusing lens Half wave-plate lens Beam splitter PBS (polarizing beam splitter) Rotation of polarization Recorded marks Track pitch Bias field coil MO film mirror ICFM2001 Crimia October 1-5, 2001

Advances in MO recording Super resolution MSR MAMMOS/DWDD Use of Blue Lasers Near field SIL Super-RENS (AgOx) ICFM2001 Crimia October 1-5, 2001

MSR (Magnetically induced super-resolution) 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 α d ICFM2001 Crimia October 1-5, 2001

Illustration of 3 kinds of MSR ICFM2001 Crimia October 1-5, 2001

AS-MO standard ICFM2001 Crimia October 1-5, 2001

iD-Photo specification ICFM2001 Crimia October 1-5, 2001

MAMMOS (magnetic amplification MO system) ICFM2001 Crimia October 1-5, 2001

Super-RENS super-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 =0.26m、mark length =213m (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=0.34m and mark length=0.29m in 35m 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) NA=1.5 405nm 80nm mark 40GB ＳＩＬhead 405nm LD I. Ichimura et. al. (Sony), ISOM2000 FrM01 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 405nm LD Recording head (SIL) Readout MR head Achieved 60Gbit/in2 H. Saga et al. Digest MORIS/APDSC2000, TuE-05, p.92. TbFeCo disk 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 fiber Signal source Laser diode module ICFM2001 Crimia October 1-5, 2001

Optical fiber amplifier and optical isolator EDFA isolators mixer Pumping laser Band pass filter output input ICFM2001 Crimia October 1-5, 2001

Optical Circulator A B C D ICFM2001 Crimia October 1-5, 2001

Optical add-drop and circulator Fiber grating ICFM2001 Crimia October 1-5, 2001

Polarization dependent isolator polarizer analyzer mag.field Faraday rotator 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 B2 B1 F C Birefringent plate B1 × Faraday rotator F 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 installation Magnetic 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. ICFM2001 Crimia October 1-5, 2001