IEEE Photonics Soc. distinguished lecture 1 Tetsuya MIZUMOTO Dept. of Electrical and Electronic Eng....

IEEE Photonics Soc. distinguished lecture1

Tetsuya MIZUMOTO

Dept. of Electrical and Electronic Eng.

Tokyo Institute of Technology

Optical Isolator:Application to Photonic Integrated Circuits

IEEE Photonics Soc. distinguished lecture 2

Bulk optical isolatormagneto-optic (Faraday) effectoperation principle

Waveguide optical isolatorTE-TM mode conversion isolatornonreciprocal loss (active) isolatornonreciprocal phase shift isolatorintegration (direct bonding)

Non-magneto-optic approach

Outline


Photon injection photon-generated carrier disturbs carrier distribution (amplitude-noise) carrier-induced index change (phase-noise)

What happens?

Isolator


Magneto-optic material

Requirement

- large magneto-optic (MO) effect --> 1-st order MO effect (Faraday rotation)

- low optical absorption

- temperature insensitive

Rare earth iron garnet (R3Fe5O12)

Y3Fe5O12 (YIG)

--> (Y3-xBix)Fe5O12, (Y3-xCex)Fe5O12

enhancement of Faraday rotation


M. Gomi, et al., J. Appl. Phys., 70(11), 7065-7067 (1991).

Characteristics of Y3-xCexFe5O12 (Ce:YIG)

Spectra of Faraday coefficient Spectra of optical absorption


Bulk isolator, in either beam interface or fiber interface, uses rotation of polarization.

Bulk isolator

Basic configuration

Polarizer

Polarizer

45degFaraday rotator

H

Polarizer

Polarizer


H

Polarizer

Polarizer


Reciprocal rotator

H

Input and output : same polarization

Namiki


Bulk isolator

Input fiber

Output fiber

Lens

Birefringent crystal

Birefringent crystal

/2 plate45deg Faraday rotator

H

Fiber in-line isolator --> Walk-off

T.Matsumoto (NTT), Trans. IECE, J62-C, 505-512 (1979).

birefringent plates polarization independent operation

FDKIsolation>35dB, IL<0.6dB

KyoceraIsolation>30dB, IL<2.5dB


Translate Faraday isolator into waveguide one.

TE-TM mode conversion type

Polarizer

Polarizer


Reciprocal rotator

H

TE-TM mode conversion Isolation:12.5 dB, l=1150 nm Length: 6.8 mm

K. Ando, T. Okoshi and N. Koshizuka (present AIST), Appl. Phys. Lett., 53(1), 4 (1988).

Faradaypart

Cotton-Mouton part

Modeselector

Magnetoopticwaveguide

M

qm


TE-TM mode conversion

Faraday rotation in a birefringent medium

Phase matched: d=bTE-bTM=0 )( Fq

zE

zE

zE

zE

FTE

TM

FTE

TE

sin)0(

)(

cos)0(

)(

Phase mismatched: 0

z

E

zE

zjzE

zE

F

F

F

TE

TM

F

F

FTE

TE

22

22

22

22

22

sin)0(

)(

sincos)0(

)(

Birefringence-free (phase matching)is essential to isolator operation.

rotates in a linearly polarized state


Waveguide isolators

type mechanism

mode conversion

filed shift

guided TE / guided TM(Faraday & Cotton-Mouton)

transversely radiated TE / guided TM(with TM nonreciprocal phase shift)

guided TE / radiated TM(semi-leaky)

nonreciprocal phase shift(interferometer)

nonreciprocal loss(active)

p-electrode

n-electrode

n+ InP sub.

GaInAsP MQWs

Al2O3 Fe

TiO2

H

Ce:YIG

LiNbO3

θ c-axis

NOG

Faradaypart

Cotton-Mouton part

Modeselector


M

θ m


T. Shintaku (NTT), Appl. Phys. Lett., 73(14), 1946 (1998).

Nonreciprocal radiation (TM phase shift)

Mode conversion: transversely leaky mode

Performance: - Isolation: 27 dB (l=1535 nm, L=4.1 mm) - wavelength sensitive (7 dB at l=1515 nm)

(TE)

(TM)

cx

cy

11by

11fy

11x

rx

Radiation modes

Propagation constant diagram

Film thickness

Pro

paga

tion

cons

tan

t

cx

cy

ay

ax

TM mode

TE mode

tatc

11x

11fy

11by

ta tc

w


Semi-leaky isolator: operation principle

LiNbO3 mode conversion reciprocalMagneto-optic mode conversion nonreciprocal (changes its sign for F/B)

Anisotropy of LiNbO3

Semi-leaky waveguide

unidirectional mode conversion

Ce:YIG

LiNbO3

c-axis

NOGTE mode

2.143

1.9382.200

H

TE mode

Ce:YIG

LiNbO3

c-axis

NOGTM mode

2.210

1.9382.200

H

TM mode

Forward -k(Ce:YIG)+k(LiNbO3)=0Backward k(Ce:YIG)+k(LiNbO3)≠0

guided

radiated Semi-leaky isolator is attractive;- relaxed fabrication tolerance - simple mono-section structure- easy control of magnetization

- but, uniform and tight LiNbO3 / garnet contact is needed.

direct bonding

S.Yamamoto, et al (Osaka U.), IEEE QE, 12, 764 (1976).


p-electrode

n-electrode

n+ InP sub.

GaInAsP MQWs

Al2O3 Fe

TiO2

H

H.Shimizu and Y.Nakano (U.Tokyo), JLT, 24, 38-43 (2006).

Nonreciprocal loss (active) isolator

Real neff

Imag

inar

y (L

oss)

kef

f

Backward

Forward

0

SOA gain

Active group:U.Tokyo, AIST, Ghent U.

Isolation: 14.7 dB/mmInsertion loss: 14.1 dB/mm (I=150 mA)


4 dB isolation at l=1543.8 nm

4 dB

15OC

Integration with active devices

nonreciprocal loss (active) excellent compatibility to active devices

p-electrode

n-electrode

n+ InP sub.

GaInAsP MQWs

Al2O3 Fe

TiO2

H

H. Shimizu and Y. Nakano (U.Tokyo), IEEE PTL, 19, 1973-1975 (2007).

active isolator0.7 mm

DFB LD0.3 mm

90mA150mA

compatible waveguide structure material & dimensions


p-electrode

n-electrode

n+ InP sub.

GaInAsP MQWs

Al2O3 Fe

TiO2

H

type Passive Active

Integration type dependent excellent

Noise none ASE

Power consumption

none current injection to SOA

Polarization dependence

yes, but can be overcome

yes

Comparison: passive and active isolators


Waveguide isolator: nonreciprocal phase shift

Interferometer type - Isolation: 19 dB (l=1540 nm, L=8.0 mm) J. Fujita, M. Levy and M. Osgood, Jr. (U.Columbia), Appl. Phys. Lett., 76(16), 2158 (2000).

- Isolation: 25 dB (l=1600 nm, L=4.0 mm) Y. Shoji and T. Mizumoto (Tokyo Tech), Optics Express, 15, 13446 (2007).

- wavelength insensitive designed to cover both 1.31/1.55 mm in a single chip Y. Shoji and T. Mizumoto (Tokyo Tech.), Optics Express, 15, 639 (2007). - polarization independent not by polarization diversity scheme Y. Shoji and T. Mizumoto (Tokyo Tech.) et al, JLT, 25(10), 3108-3113 (2007).


-/2 - j/ 2 21 /

21 /

21 /

21 /

j/ 2

Output

Reflected

Input

Forward (constructive interference)

Backward (destructive interference)

2-1 /

21 /

21 /

21 /

/2 phase bias

/2

Single polarization operation

→ No need for phase matching

→ Fabrication tolerant Simple in-plane magnetization

Interferometric isolator: operation principle

Interferometric isolator


Nonreciprocal phase shift = (b+-b-) (m-1)

Nonreciprocal phase shift

1st–order MO effect

2

222'2

2

'2

2'2

23

3

1

1

3

3

1

1

2

'2

3

3

1

1'2

)tan(

y

zy

yy

n

nn

nn

ppppq

ppq

qd

linear in b

y z

x

2

2

2

2

0

00

0

j

j




0 0.2 0.4 0.6 0.8 10

1.0

2.0

Thickness of Ce:YIG guiding layer [mm]

NP

S/(p

/2)

[mm

-1] l=1550nmTM0 mode d (CeY)3Fe5O12

SGGG (n=1.94)

SiO2 (n=1.45)

cutoff


1.45 1.5 1.55 1.6 1.65

0

0.1

0.2

0.3

0.4

0.5

Wavelength (mm)

For

war

d lo

ss (

dB)

Interferometric isolator: calculated performance

1.45 1.5 1.55 1.6 1.65

0

10

20

30

40

50

Wavelength (mm)

Bac

kwar

d lo

ss (

dB)


Cancellation of wavelength dependences in backward propagationY.Shoji and T.Mizumoto (Tokyo Tech.), Appl. Opt., 45, 7144 (2006).

l dependences : MO effect waveguide dispersion

Interferometric isolator: wideband operation

wideband design

Ph

ase

shift

qR

ll0

qN(backward)

qN (forward)

q (backward)p

/2p

- /2p

3 /2p

2p q (forward)

0

Conventional design

Ph

ase

shift

qR

ll0

qN(backward)

qN (forward)

q (backward)p

/2p

- /2p

q (forward)0


Larger isolation in wider wavelength range

1500 1550 1600 1650

30

20

10

0

Wavelength (nm)

atte

nuat

ion

(dB

)

forward backward

1500 1550 1600 1650

30

20

10

0

Wavelength (nm)

atte

nuat

ion

(dB

) forward backward

Conventional designWideband design

Wideband design: experimental results

Y. Shoji and T. Mizumoto (Tokyo Tech.), Optics Express, 15, 13446 (2007).

• measured with a reference of 　 straight waveguide (5 ｄ B loss)


930m

493m

26m 300m

665m

2.0m

3.0m

L/2

665m

Wideband design covers fully 1310 nm / 1550 nm bands and more.

Isolation > 40 dB :

@ 1260-1650 nm

1.3 1.4 1.5 1.6

50

40

30

20

10

0

Wavelength [mm]

atte

nua

tion

[dB

]

1.55 mm Forward

1.31-1.55 mm Forward1.55 mm Backward

1.31-1.55 mm Backward

Ultra-wideband design

Y. Shoji and T. Mizumoto (Tokyo Tech.), Optics Express, 15, 639 (2007).


Photonic integrated circuit: device and material

- photonic integrated circuit waveguide alignment lithography process materials to be grown (deposited) on a common platform

LD, SOAIII-V semiconductor

modulator, SWLiNbO3,

III-V semiconductor

l-MUX/DeMUXSilica

IsolatorMagneto-optic material


Common semiconductor guiding layer (selective growth & mask process)

Our approach: integration of isolator and LD

Direct bonding

H. Yokoi and T.Mizumoto (Tokyo Tech.), Electron. Lett., 33, 1787 (1997).

LD integrated with isolator

compatible waveguide structure material & dimensions

Single polarization operation


III-V waveguide isolator




1

221'

1

3'11

3

3

3'

1

1

2

2

'113

3'

1

1

2)tan(

pppq

ppq

qd

linear in b

y z

x

1st–order MO effect

1

1

1

1

0

00

0

j

j

0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

GaInAsP thickness (m)

Non

reci

proc

al p

hase

shi

ft (m

m-1

)Q1.42 (n=3.45)

Q1.25 (n=3.36)

=1.55mTM0mode

qF=-4500deg/cm


Bonding garnet on III-V

III-V MO garnet

crystal structure zinc blende garnet

lattice constant (A) 5.869 (InP) 12.54

thermal expansion (K-1) 4.56 X 10-6 (InP) 9.20 X 10-6

refractive index 3.2 – 3.5 2.2

n(garnet) < n(III-V) Evanescent field is to be used in MO garnet.

direct bonding with no gap in-between

garnet

InP

GaInAsP

Challenging: epitaxial growth of III-V on garnet done by Dr. M. Razeghi (Thomson), JAP, 59, 2261 (1986) and Dr. J. Haisma (Philips), J. Cryst. Growth, 83, 466 (1987)


Surface activated bonding

Surface activation in vacuum chamber


Direct bonding: garnet on GaInAsP/InP waveguide

Bonding strength Fracture in an InP substrate at a tensile > 0.5 MPa

Ce:YIG / GaInAsP

T.Mizumoto, et al, ECS Meeting, 1258 (2006).

Ce:YIG

GaInAsP

Low temperature heat treatment


Si-waveguide isolator

L=364mm

MMI

R=2.5mm


Nonreciprocal phase shift (NPS):Db = b+ - b-

External magnetic field

SiO2

Ce:YIG

Si Ce:YIG

SiSiO2

xy

z

Ex External magnetic field

TM mode

Lp/2 (Min) ~300mm @0.2-mm-thick

CeY2Fe5O12 (Ce:YIG) ： QF = -4500 deg/cm

H.Yokoi, et al (Tokyo Tech.)., Applied Optics, 42, 6605-6612 (2003)

0 0.2 0.4 0.6 0.8 110-1

100

101

Thickness of guiding layer (m)

Non

reci

proc

al p

hase

shi

ft (m

m-1

)

Ce:YIG on SOI

Ce:YIG on GaInAsP (n=3.45)

=1.55m, TM0mode

Nonreciprocal phase shift in SOI WG


Si-waveguide optical isolator

4.0mmSOI

Ce:YIG

Rib waveguide for reducing propagation loss (trial fabrication)

Bonding condition　 Anneal: 250 oC Press: 5 MPa, 1 hour

H.Yokoi, et al (Tokyo Tech.)., Applied Optics, 42, 6605-6612 (2003)

300Si

SiO2

Si 2mm10nm

Ce:YIG

300nm

Si rib waveguide

Ce:YIG

SGGG


3-pole magnet --> anti-parallel magnetic field (S-N-S or N-S-N)

2X2 optical SW --> reverses propagation direction (CWCCW)

ASE source

N

S

S

Spectrum Analyzer

PMF PMF

TM mode

IR cameraTV

monitor

Polarizer

lens

Optical switch

CW

CCW

Sample

Measurement setup


First demonstration of Si waveguide isolator !

The interference reverses as the propagation direction is reversed.

First demonstration of Si-waveguide isolator

Y. Shoji, T. Mizumoto (Tokyo Tech), et al. APL, 92, 071117 (2008).

The interference reverses as the magnetic field directions are reversed.

1530 1540 1550 1560 1570-70

-60

-50

-40

Wavelength (nm)

Tra

nsm

ittan

ce (

dB)

w/o H field

CCW

CW

Mag: N-S-NMag: N-S-N

1530 1540 1550 1560 1570-70

-60

-50

-40

Wavelength (nm)

Tra

nsm

ittan

ce (

dB)

Isolation: 21dB

CW

CCW

Mag: S-N-SMag: S-N-S

N-S-N

S-N-S


(a) Coupling loss between fiber and waveguide x2 : 37 dB(b) Propagation loss : 4 dB Si waveguide (2.5 dB / 4 mm) + Absorption of Ce:YIG (0.2 dB) + reflection at bonding boundary (0.65 dB x2) (c) Excess loss of MZI : 4 dB

Insertion loss of the isolator ((b)+(c)) : 8 dB

Si-waveguide isolator: insertion loss

MZI

Single WG

Ce:YIG upper clad

2.0 mm4.0 mm1530 1540 1550 1560 1570

-70

-60

-50

-40

wavelength (nm)

tra

nsm

ittan

ce (

dB) (a)

(b)(c)

21dB Isolation



“Indirect photonic transition”

Zongfu Yu and Shanhui Fan (Stanford), Nature Photonics, 3, 91-94 (2009).

Backward: Mode-1 (w1, -k1) is coupled to mode-2 (w2, -k2).

(-k1 - q = -k2 , w2-w1=W : phase-matched) --> transition

mode-2 (w2, -k2) filtered out

Forward: Mode-1 (w1, k1) is uncoupled to mode-2 (w2, k2).

(k1 - q > k2 , phase-mismatched) --> no transition

-3 -2 -1 0 1 2 30

0.2

0.4

0.6

0.8

1

kz (2p/q)

w(2

pc/

a) W

w1

w2

k1

k2

-k1

-k2



Traveling wave (dynamic) modulation

Z. Yu and S. Fan (Stanford), Nature Photonics, 3, 91-94 (2009).

Backward: effective coupling e(z,t)=d cos( W t - (-q)z) -k1 - q = - k2

w2-w1=W

Example (l=1550 nm): /d e=5x10-4, f=20 GHz w=0.27 mm, L=2.19 mm

0-th 1-st

z

t0t0+t

Mod

ulat

ion

-

0

0 2/q


Summary

Optical isolators for photonic integrated circuits

★ Mode conversion isolator requirement of phase matching limited fabrication tolerances

★ Interferometric isolator single polarization operation no need for phase matching ultra-broad band operation (1.31/1.55 mm in a single chip)

integration with active devices Ce:YIG/ III-V, Ce:YIG/ Si low-temperature direct bonding

first demonstration of Si waveguide isolator 21 dB isolation

★ Non-magneto-optic approach attractive (less restricted by material), but still challenging


Semi-leaky isolator: performance

Measured isolation : 20.2 dB / 1.5 mm=13.5 dB/mm

20.2 dB

W=3 mm

1.5 mm

4.5 mm

Externalmagnetic field(Electromagnetic Coil)

PowermeterPMF

Tunable laserl=1550 nm

PM

F

Polarizer

constant coupling loss (-15 dB/facet)

T.Mizumoto et al, IEICE Trans, J89-C, 423 (2006).T.Mizumoto et al, OFC2007, OThU4 (2007).


Part-1: Bulk nonreciprocal devicesmagneto-optic effect (Faraday rotation)operation principle of isolators and circulators

Part-2: Waveguide isolators operational principles, design and characterization

TE-TM mode conversion isolatorsNonreciprocal loss isolatorInterferometric isolatorSemi-leaky waveguide isolator

Part-3: Waveguide circulators

Part-4: Non-magneto-optic approach

Outline


z

r

r

j

j

00

0

0

0

Faraday effect

jEE jiE )(0 r rk0

jEE jiE )(0 r rk0

Faraday rotator

Hx

y

z

Dielectric tensor

Circular polarization

CW:

CCW:


Faraday effect

ztzEEx 2cos

2cos0

ztzEEy 2cos

2sin0

Linearly polarized wave --> two circular polarized components

CW circular polarized CCW circular polarized

Faraday rotator

H

2

coscos22

coscos2

00 ztztE

zttztE

jiji

zk

z

rr

F

)(2

2

0


Faraday rotator

Hx

y

z

Faraday rotator

HBackward

Faraday rotator

HForward

Faraday effect

Hx

y

z

Reversal of H-field

FrrF

k )(

20

H

xy

z

Reversal of propagation direction


Waveguide Faraday rotator

E. Pross, et al. (Philips) , APL, 52(9), 682 (1988).

N. Sugimoto, et al. (NTT) , APL, 63(9), 2744 (1993).


Isolator

Isolator - two-port device - includes loss mechanism

#1 #2

01

00S

10

00*tSS non-unitary matrix --> lossy







Outline


Circulator

Circulator - many-port device - lossless device

#1 #2

#3

010

001

100

S

100

010

001*tSS unitary matrix --> lossless


Optical circulator

H.Iwamura, et al, Electron. Lett., 15, 830-831 (1979).

- uses rotation of polarization- polarization independent operation







Outline




Faradaypart

Cotton-Mouton part

Modeselector


M

θ m

Faraday rotation

sin)0(

)(

sincos)0(

)(

q

κj

E

zE

qj

E

zE

*

TE

TM

TE

TE

zzqz

jn

kj

F

F

2

TMTE222

0

TMTE

2

2

2

qF : Faraday rotation, G : field confinement factor

Phase mismatch







Outline




y z

x

00

000

00

j

j

MO perturbation

dSHn

dSHxn

dS

dSHxn

dS

dSEx

dS

dS

y

y

z

y

z

x

z

2

2

2

4

**

2

4

0

**

2

0

**

*

0

12

2

2

HEHE

HEHE

HEHE

EE


Interferometric isolator: polarization-independent

(1-η )TM0° (1-η )TM0°

(1-η )TM0°

(1-η )TM180°

(1-η )TE0°

(1-η )TE0°

(1-η )TE0°

(1-η )TE0°(1-η )TE0°(1-η )TE0°

(1-η )TM-180° (1-η )TM0°(1-η )TM-180°

(1-η )TM0°

MC1

N

MC2

MC1

N

MC2

MC1

N

MC2

MC1

N

MC2

180

180

180

180

TM0°

η TE0°η TE0°

TM0° η TE0°

2TM

TM0°

2TE

TE0°

TE0°

η TM0° η TM0°

TE0° η TM0°

2TE

η TM0°

TE0°TE180°

η TM -180°

η TM180°

2TM

TM0°TM180°

η TE0°η TE0°

η TM -180°

TM0°η TE0°

η TE0°

η TE180°

η TM180°

2η TM

2η TE

TE0°

TE180°

(b)

(a)

(c)

(d)

(1-η )TE180°

(1-η )TE 180°

N: nonreciprocal phase shifter provides NPS only for TM mode MC: mode converters provide TE-TM mode conversion

Y. Shoji and T. Mizumoto (Tokyo Tech.) et al, JLT, 25(10), 3108-3113 (2007).


Issues to be considered・ surface treatment → hydrophilic・ mismatch in thermal

expansion coefficient → low temperature

heat treatment

・ Si / Si・ Si/SiO2 / Si,・ III-V(GaAs,InP) / Si,・ III-V(GaAs, GaP, InP,

InAs) / III-V・ Ce:YIG / III-V・ Ce:YIG / SiO2

・ Ce:YIG / LiNbO3

Hydrophilic bonding


Surface treatment

(GdCa)3(GaMgZr)5O12(111)

Heat treatment in H2 atmosphere

H3PO4 (RT)

temperature 220ºC

Deionized water

Deionized water

InP (100)

GaInAsP (λ g=1.25m)

O2 plasma (30s)

E-beam lithography

O2 plasma (30s) or

GaInAsP

Sputter epitaxy(CeY)3Fe5O12

pressure 0.025 MPa

CH4/H2 RIE

Hydrophilic bonding: fabrication


Input

Output


NS

NS

NSN

Input

Output


SN

SN

SNS

Isolation 4.9 dB

Semiconductor waveguide isolator: demonstration

H. Yokoi, et al (Tokyo Tech.), Appl. Opt, 39, 6158 (2000).


Ideal MMI couplers

Y.Shoji, T.Mizumoto, et al., APL, 92, 071117 (2008)

1530 1540 1550 1560 1570

-50

-40

-30

-20

-10

0

Wavelength (nm)

Tra

nsm

issi

on lo

ss (

dB)

Lasym =0 mm

Lasym =111 mm

Forward

Backwardperfectly balanced

slightly unbalanced

Calculated characteristics







Outline


Mode conversion: semi-leaky

Semi-leaky type

Isolation: 20.2 dB (l=1550 nm, L=1.5 mm) - fabrication tolerant - wavelength insensitive

proposed by S. Yamamoto, et al (Osaka U.),IEEE QE, 12, 764 (1976).

T. Mizumoto et al.(Tokyo Tech), OFC 2007, OThU4 (2007).

Ce:YIG

LiNbO3

θ c-axis

NOGTE mode

2.143

1.9382.200

H

TE mode

Ce:YIG

LiNbO3

θ c-axis

NOGTM mode

2.210

1.9382.200

H

TM mode

guided

radiated

Mode conversion - TE-guided and TM-radiation modes - MO and LN mode conversions


Semi-leaky isolator: design

1.0 2.0

10

20

30

40

50

0

10

20

30

40

0Guiding layer thickness [ m]

Off

set

angl

e [

deg]

Isol

atio

n [

dB/m

m] = 1.55 m

Offset angle

Backward lossTo cancel mode conversion in forward direction offset angle of LiNbO3

Mode conversion in backward direction isolation

Ce:YIG

LiNbO3

θ c-axis

NOG

Isolation = 14.1 dB/mmfor 50dB isolation : L=3.5 mm

Ce:YIG qF=-4500 deg/cm


1 1.1 1.2 1.30

10

20

0

1.0

2.0

Guiding layer thickness [ m]

Bac

kwar

d lo

ss /

Isol

atio

n [d

B/m

m]

Foward loss

Backward loss

Isolation

=1.55m

Fow

ard

loss

[dB

/mm

]

Radiation modes

-diagram

/k0(TE)

LiNbO3

ne=2.143

LiNbO3

no=2.210

Ce:YIGn=2.200

/k0(TM)

Guided mode

1.45 1.5 1.55 1.6 1.650

10

20

0

1.0

2.0

Wavelength [m]

Bac

kwar

d lo

ss/I

sola

tion

[dB

/mm

]

Forward loss

Backward loss

Isolation

For

war

d lo

ss [

dB/m

m]

1500nm < l < 1600nm: Isolation >12.5dB/mm Forward loss < 0.09dB/mm

Semi-leaky isolator: calculated performance


Semi-leaky isolator: fabrication

x-cut LiNbO3

Ce:YIG waveguide&terraceGarnet No.CY0523

4.5mm

Bonding completed

Time : 3 minAnneal : none (RT)

Positioning : ~ 10 min

Hig

h va

cuum

Sample set

Pressure : 4.0 Pa (= 3.0x10-2 Torr)Gas flow : O2 2 sccm

Ar 20 sccmRF power : 250 WTime : 5 min

RF plasma : Ar + O2

Press : ~ 1MPa

Vacuum : 6.0x10-7 Pa Ce:YIG

LiNbO3

θ c-axis

NOG


Semi-leaky guiding characteristics

Semi-leaky guiding characteristic

partially guided

TE mode

Ce:YIG

LiNbO3

c-axis

NOG

radiated

TM mode

Ce:YIG

LiNbO3

c-axis

NOG







Outline


Waveguide optical circulator: TE-TM Mode conversion

- uses TE-TM mode conversion (rotation of polarization plane)

N. Sugimoto, et al. (NTT), IEEE PTL, 11, 355-357 (1999).


#4#3

#2#1

Waveguide optical circulator: operation principle

#4

#1

#4#2


Waveguide optical circulator: performance

#1#2

#3#4

out in #1 #2 #3 #4

#1 -- 17.1-19.5 3.2-3.3

#2 -- 3.1-3.2 17.2-18.7

#3 3.0-3.1 26.4-31.4

#4 27.0-31.8 3.0-3.1 --

N. Sugimoto, et al. (NTT), IEEE PTL, 11, 355-357 (1999).

Measured transmittance (dB)


Waveguide optical circulator: Interferometric circulator

Direction-A (in-phase interference)

Direction-B (out-of-phase interference)

T. Mizumoto, et al. (Tokyo Tech.), EL, 26, 199-200 (1990).







Outline


Interferometric isolator - single polarization operation --> no need for phase matching - ultra-wide band operation (1.31 / 1.55 mm in a single chip)

- integration with active devices --> Ce:YIG/ III-V, Ce:YIG/ Si low-temperature direct bonding

- first demonstration of Si waveguide isolator --> 21 dB isolation

Semi-leaky waveguide isolator - highly fabrication tolerant - LN/Ce:YIG direct bonding - 20 dB / 1.5 mm

Summary 2


Waveguide circulator

Hybrid Faraday rotation type

MZ interferometer


dynamic modulation - indirect photonic transition of eigen modes dependent on propagation direction

Summary 3

IEEE Photonics Soc. distinguished lecture 1 Tetsuya MIZUMOTO Dept. of Electrical and Electronic Eng....

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Transcript of IEEE Photonics Soc. distinguished lecture 1 Tetsuya MIZUMOTO Dept. of Electrical and Electronic Eng....