集成平面光波導(dǎo)器件 - 光調(diào)制器

《集成平面光波導(dǎo)器件》課程Chapter

13:

Optical

Modulators

Optical

Modulation

光調(diào)制就是將一個(gè)攜帶信息的信號(hào)疊加到載波光波上,完成這一過程的器件稱為調(diào)制器。

直接調(diào)制(內(nèi)調(diào)制)：把承載信息的電信號(hào)作為驅(qū)動(dòng)電流直接施加在激光器上即以調(diào)制信號(hào)去改變激光器的振蕩參數(shù)，從而改變激光輸出特性以實(shí)現(xiàn)調(diào)制

2

Direct/External

Modulation?Direct

Modulation

of

Laser

DiodeBias

+

DATA驅(qū)動(dòng)電流

LD或LED?

Laser

Carrier

induced

(chirp)Temperature

variation

due

to

carrier

modulationExternal

Modulation

of

Laser

Diode

BiasLaser

Bias

+

DATAModulator《集成平面光波導(dǎo)器件》課程Issues

--

Additional

ComponentC

直流偏置

Direct

Modulation半導(dǎo)體激光器調(diào)制原理以及輸出光功率與調(diào)制信號(hào)的關(guān)系曲線。為了獲得線性調(diào)制，使工作點(diǎn)處于輸出特性曲線的直線部分，必須在加調(diào)制信號(hào)電流的同時(shí)加一適當(dāng)?shù)钠秒娏鱅b，這樣就可以使輸出的光信號(hào)不失真。

t輸出光強(qiáng)信號(hào)LD輸出功率

L~

調(diào)制信號(hào)(a)直流偏置

t調(diào)制信號(hào)

(b)半導(dǎo)體激光器調(diào)制

(a)

電原理圖；(b)

調(diào)制特性曲線

4PoutDirect

Modulation

PouttIOIOIbID

t(b)t(a)(a)

LED數(shù)字調(diào)制特性(b)

加Ib后LD數(shù)字調(diào)制特性5

External

Modulation

外調(diào)制：通過光調(diào)制器，將攜帶信息的電信號(hào)與輸入光調(diào)制器的連續(xù)光載波相作用。包括：幅度調(diào)制、頻率調(diào)制、相位調(diào)制、偏振調(diào)制。

電信號(hào)激光器光載波調(diào)制光信號(hào)輸出外調(diào)制器

外調(diào)制方式6Direct/External

Modulation

信息

電信號(hào)激光器

輸出調(diào)制光

連續(xù)光信號(hào)外調(diào)制器激光器

輸出調(diào)制光信息電信號(hào)LD

輸出連續(xù)光信息電信號(hào)01

010信息電信號(hào)輸出調(diào)制光波輸出調(diào)制光波01

0

1

0（a）

直接調(diào)制（b）外調(diào)制直接調(diào)制：電路簡單，容易實(shí)現(xiàn)，高速率時(shí)輸出光光譜變寬，易受光纖色散影響；外調(diào)制：適合高速率光纖傳輸系統(tǒng)7Optical

Modulator

光調(diào)制器---外調(diào)制方式中采用，把激光的產(chǎn)生和調(diào)制分開，

可避免對光源直接調(diào)制產(chǎn)生線性調(diào)頻的限制。調(diào)制器能使載波光波的參數(shù)隨外加信號(hào)變化而變化，這些參數(shù)包括光波的振幅、位相、頻率、偏振等。承載信息的調(diào)制光波在光纖中傳輸，再由光探測器系統(tǒng)解調(diào)，然后檢測出所需要的信息。與光開關(guān)的區(qū)別：如果一個(gè)器件的主要作用是通過暫時(shí)改變光波的某一特性將信息加到光波上去，則為調(diào)制器；而光開關(guān)則是改變光線的空間線路或控制其通斷。8

Optical

Modulator

1.

調(diào)制帶寬f3dB:

光調(diào)制器的頻域響應(yīng)類似與低通濾波器，其

帶寬對應(yīng)與光調(diào)器的響應(yīng)度減小到一半時(shí)的微波頻率。

2.

消光比

3.

插入損耗:

表征光經(jīng)過調(diào)制器時(shí)光功率的損失，包

括耦合損耗和傳速損耗。

4.

能耗:

定義為單位比特所需消耗的能量。

半波電壓光纖通信系統(tǒng)對調(diào)制器的要求高的調(diào)制速率

寬的調(diào)制帶寬

低的半波電壓

高的消光比低的插入損耗《集成平面光波導(dǎo)器件》課程

Optical

ModulatorElectro-Optic

Modulator

(LiNbO3)

Semiconductor

based

Modulator(EA,

Si

Modulator)

Others(Polymer,

Slot

Waveguide,

PhCs,

Graphene)《集成平面光波導(dǎo)器件》課程Electro-Optic

Modulation《集成平面光波導(dǎo)器件》課程Pockels

Effect/Kerr

Effect《集成平面光波導(dǎo)器件》課程EO

Phase

Modulator《集成平面光波導(dǎo)器件》課程EO

Phase

Modulator《集成平面光波導(dǎo)器件》課程EO

Phase

Modulator《集成平面光波導(dǎo)器件》課程EO

Intensity

Modulator《集成平面光波導(dǎo)器件》課程《集成平面光波導(dǎo)器件》課程Optical

Modulator-EOM-Z型LiNbO3調(diào)制器是目前光通信中實(shí)用的電光調(diào)制器輸入光信號(hào)在C處被分為相等的兩束，分別進(jìn)入兩波導(dǎo)傳輸。波導(dǎo)的折射率隨外加電壓大小而變化，導(dǎo)致兩路光信號(hào)到達(dá)D時(shí)的相位延遲不同。若兩束光光程差是半波長的偶數(shù)倍，兩束光相干加強(qiáng)；若是半波長的奇數(shù)倍，則兩束光相干抵消，輸出很小。因此，控制外加電壓，就能實(shí)現(xiàn)光調(diào)制。17用LN晶體制作的M-Z調(diào)制器n

E

n

2

2

n3

VL

0

0d

T

cos

(

Optical

Modulator-EO波導(dǎo)臂上產(chǎn)生的折射率變化1

3

1

3

V2

2

d

n

對于對稱型M-Z干涉儀，L1=L2=L，兩臂的相位差為

（2

n）L

令

＝

時(shí)的電壓為半波電壓

V

V

0d2n3

L)2

V

V2V

18Optical

Modulator-EO

電光調(diào)制的透過率(調(diào)制器被偏置在V

/2點(diǎn)上)

透射光強(qiáng)t

VV

/2V

調(diào)制電壓半波電壓V

是把調(diào)制器從最小光

強(qiáng)轉(zhuǎn)換到最大光強(qiáng)所需的電壓《集成平面光波導(dǎo)器件》課程注意：在調(diào)制的區(qū)域要求器件的線性度高。若調(diào)制器工作在非線性部分,則調(diào)制光將發(fā)生畸變。Optical

Modulator-EO《集成平面光波導(dǎo)器件》課程Optical

Modulator-EOData

From:

《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO

Techniques

for

Down

Sizing-

reduction

the

driving

voltage

Ridge

Waveguideinstead

of

Diffused

Waveguide《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO

Techniques

for

Down

Sizing-

reduction

the

driving

voltage《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO《集成平面光波導(dǎo)器件》課程Optical

Modulator-EOFrequency

Response

of

an

Over-40

Gbps

Modulator

《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO《集成平面光波導(dǎo)器件》課程Optical

Modulator-EO《集成平面光波導(dǎo)器件》課程Optical

intensityOptical

modulation-Semiconductor

ElectricaldriverModulated

opticalintensityt

OpticalmodulatorttElectroabsorption

Quantum

Confined

Stark

effect

Franz-Keldysh

effect

Electrorefraction

Free

carrier

concentration

variations

in

silicon

AccumulationInjectionDepletion《集成平面光波導(dǎo)器件》課程29Optical

modulation-Semiconductor

?

基于半導(dǎo)體材料的調(diào)制器的工作本質(zhì)是通過

電信號(hào)改變介質(zhì)的復(fù)折射率。

?介質(zhì)的復(fù)折射率為:

~

n

jnn

r

i基于改變折射率nr的調(diào)

制器稱為

折射率型光調(diào)制器基于改變折射率需不

虛部的調(diào)制器稱為

電吸收型調(diào)制器

《集成平面光波導(dǎo)器件》課程Modulator-Electro-absorption《集成平面光波導(dǎo)器件》課程Franz-Keldysh

effect（弗蘭茨－凱第希效應(yīng)）Energy

band

diagram

of

a

semiconductor

exhibiting

the

Franz-Keldysh

effectin

the

presence

of

a

strong

electric

field.The

parameter

x

represents

the

distance

from

the

surface

of

thesemiconductor,

and

E

is

the

electron

energy.

Ec

and

Ev

are

the

conduction

andvalence

and

edges,

respectively.

《集成平面光波導(dǎo)器件》課程Franz-Keldysh

effectCurve

A

is

the

zero

field

absorption

curve

forGaAs.(Circular

dots

represent

experimentaldata

points

for

n-type

material

with

carrierconcentration

n=3x1016cm-3.

For

the

squaredot

n=5.3x1016cm-3)

Curve

B

shows

theshifted

absorption

edge

for

a

field

of1.3x105V/cm.A

very

effective

electro-absorption

modulatorcan

be

made

for

light

of

slightly

less

thanbandgap

wavelength.In

the

presence

of

a

strong

electric

field,

theabsorption

edge

of

a

semiconductor

is

shifted

tolonger

wavelengthvery

large

changes

in

absorption

of

wavelengthnear

the

band

edge

can

be

produced

byapplication

of

an

electric

field《集成平面光波導(dǎo)器件》課程Franz-Keldysh

shift

of

the

absorption

edge

of

GaAs.Franz-Keldysh

effectAluminum

concentration

b

in

the

waveguide

should

be

chosen

so

that

the

absorptionedge

wavelength

is

just

slightly

shorter

than

the

guided

wavelength,

i.e.,

the

guide

istransparent

with

V=0.

Carrier

concentrations

should

be

chosen

so

thatN3>>N2,

thus,

a

relatively

large

electric

field

is

produced

in

the

guide

when

V

isapplied.

《集成平面光波導(dǎo)器件》課程Franz-Keldysh

effectDevice

Structures

《集成平面光波導(dǎo)器件》課程Franz-Keldysh

effect《集成平面光波導(dǎo)器件》課程Quantum

Confined

Stark

effect（量子限制Stark效應(yīng)）《集成平面光波導(dǎo)器件》課程Quantum

Confined

Stark

effect《集成平面光波導(dǎo)器件》課程Optical

Modulator-EA

Extinction

Ratio:

Insertion

Loss:

Modulation

Efficiency:《集成平面光波導(dǎo)器件》課程Optical

Modulator-EA

Reported

III-V

EAM

with

a

bandwdith

over

30GHz

after

2004《集成平面光波導(dǎo)器件》課程Optical

Modulator-III-V

EA集總電極行波電極UCSB.

Y.B

Tang,

40GbpsUCSB.

Y.B

Tang,

50Gbps在高頻時(shí)，微波信號(hào)的波長和電極的長度可以比擬，因此需要將電極看成是傳輸線。利用行波電極，既能使器件的內(nèi)部等效RC常數(shù)減小，也能使光波和微波信號(hào)的速度匹配從而提高調(diào)制器的帶寬。

《集成平面光波導(dǎo)器件》課程Optical

Modulator-III-V

MZM

Reported

III-V

MZM

with

a

bandwdith

over

30GHz

after

2004

capacitively

loaded

TW

electrode(High

impedance,

low

RF

loss,

velocity

match)

《集成平面光波導(dǎo)器件》課程Klein

et

al.

(IPRM

2006)Modulator-III-V

QPSK

modulatorQPSK

constellation80Gb/s80Gb/s

QPSK

modulator

based

onnested

40GHz

III-V

MZMs(traditional

structure)《集成平面光波導(dǎo)器件》課程N(yùn).Kikuchi,

et.

al.,

PTL

21(12),

2009E1

2E

0,1

E2

E

(

1

j)E3

2

jE

0,1

Optical

Modulator-III-V

QPSK

modulator107Gb/s

1

2

(0,1)(0,0)

(1,1)(1,0)Compact

107Gb/s

QPSKmodulator

based

on

two

III-VEAMs

embedded

in

a

three-arminterferometer《集成平面光波導(dǎo)器件》課程C.Doerr,

et.

al.,

PTL

19(15),

2007Optical

Modulator-Si

PlatformPIPIN

diodeMetal

P‐doped

region

MetalN‐doped

region45Europe:

PSUD-IEF,

Surrey

Univ.

…Asia:

A*Star,

Petra,

AIST,

Chinese

Academy

ofSciences,

Samsung

Electronics,

Tokyo

Institute

ofTechnology

…North

America:Intel,

IBM,

Cornell,

Luxtera,

Ligthwire,

Kortura,

Oracle

…

《集成平面光波導(dǎo)器件》課程

Silicon

Modulators×

Kerr

Effect:

n=10-4@100V/

m×

Franz-Keldysh

effect:

~

1.1

m×

Thermal-Optic

effect:

1.86×10

-4/K√

Free

carrier

Plasma

dispersion

effect《集成平面光波導(dǎo)器件》課程

n

ne

nh=-

8.8

10-22

ne+8.5

10-18

nh

e

h=

8.5

10-18

ne

h

n

ne

nh=-

6.2

10-22

ne+6.0

10-18

nh

e

h=

6.0

10-18

ne

h

Free

carrier

Plasma

dispersion

effect

e

is

the

electron

charge,

c

is

the

light

velocity

in

vacuum,

ε0

is

the

vaccum

ermittivity,

λ

is

the

wavelength

in

vacuum,

n

is

the

refractive

index

of

intrinsic

silicon,

mce*

and

mch*

are

the

electron

and

hole

effective

masses,

μe

and

μhare

the

electron

and

hole

mobilities.當(dāng)載流子濃度為5×10

17時(shí)，折射率變化達(dá)到10-3量級(jí)

《集成平面光波導(dǎo)器件》課程Drude–Lorenz

equation:

1550

nm：

0.8

+6.0

10-18

n

1310

nm：

0.8

+4.0

10-18

n

Silicon

Modulators

Free

carrier

Plasma

dispersion

effect

Carrier

accumulationThe

performance

of

the

freecarrier

plasma

dispersion

basedsilicon

modulator

is

essentiallydetermined

by

how

fast

and

howefficiently

the

free

carrier

densityis

modulated

in

the

area

whereoptical

mode

is

traveling.

Charging/discharging

over

a

capacitor.

Serious

RC

limit,

less

efficientCarrier

Injection

Forward

bias

Relative

efficient,

Slow

diffusion

processCarrier

Depletion

Reverse

bias

less

efficient,

fast

process《集成平面光波導(dǎo)器件》課程G.T.Reed,

et

.al.

Nat.

Photon

.

4,

518-526,2010Carrier

DepletionOptical

modulator-Si

Phase

shifters:

PN

diode

Figures

of

merit

Interleaved

PN

diode

PIN

diode

PIPIN

diodePIN

diodePIPIN

diode

V

L

ILfcERModulation

efficiencyInsertion

loss‐3dB

bandwidthExtinction

ratio

Interferometers

Ring

resonator

Voltage

swing

Power

consumption

Mach-Zehnder

Photonic

crystals《集成平面光波導(dǎo)器件》課程49Silicon

Modulators-Carrier

accumulationApply

VD

to

poly.

Charge

accumulation

on

both

sides

of

gate

oxide.

Ne

=

Nh

=

[

/etoxt]*(VD

–

VFB)

ne

=

-8.8

x

10-22

Ne

nh

=

-8.5

x

10-18(

Nh)0.8

=

(2

/

)

neffL

《集成平面光波導(dǎo)器件》課程Silicon

Modulators-Carrier

InjectionVD

is

applied

to

Anodevs.

Cathode.→

forward

biased

p-i-njunction.→

e

and

holes

injectedinto

guiding

region→

changes

refractiveindex《集成平面光波導(dǎo)器件》課程Silicon

Modulators-Carrier

Injection載流子濃度分布N+區(qū)深度影響

《集成平面光波導(dǎo)器件》課程Optical

Modulator-Si

Platform《集成平面光波導(dǎo)器件》課程Silicon

Modulators-Carrier

depletion3x1018cm-31.5x1017

cm-31x1020cm-3《集成平面光波導(dǎo)器件》課程Optical

Modulator-Si

PlatformMach-Zehnder

InterferenceHigh

Q

Structure

(Ring,

FP

etc)1,

wide

optical

bandwidth2,

high

speed

operation1,

large

footprint2,

pretty

large

power

consumption

Intel

2007,

OE.

15(2),

660;1,

very

compact2,

enhanced

ER/Voltage1,

environmental

sensitivity2,

small

optical

bandwidth/EObandwidth

limited.3,

high

resolution

lithographyrequired.

Cornell

2005,

Nat.

435,

325.

《集成平面光波導(dǎo)器件》課程Optical

Modulator-Si

PlatformMach-Zehnder

InterferenceHigh

Q

StructureIntel

2004,

Nat.

427,

616Intel

2009,

AOT,

ID

67894810Gb/s,

f3dB

:

10GHz,Vpp=1.1V,

ER=3.8dBVπL:

33

V

mmCornell

2005,

Nat.

435,

325Cornell

2007,

OE

15(2),

43012.5Gb/s,

Vpp=8V,

ER=9dBf3dB

:~1GHz,Pre-emphasis

to

16VIBM

2004,

OE.

15(25),

1710610Gb/s,

f3dB

:

~1GHz,Vpp=1.2V,

ER=?dBPre-emphasis

to

7V.VπL:

0.36V

mmIntel

2007,

OE.

15(2),

660Intel

2009,

AOT,

ID

678948Kotura

2009,

OE

17(25),

2248410Gb/s,

f3dB

=

11GHzVpp=2V,

ER=6.5dB《集成平面光波導(dǎo)器件》課程40Gb/s,

f3dB

:

33GHz,Vpp=6.2V,

ER=1.1dBPre-emphasis

to

7V.VπL:

40V

mmOptical

Modulator-Si

Platform《集成平面光波導(dǎo)器件》課程Optical

modulator

Space

charge

extension

due

to

carrier

depletion

is

limited

~100

nm

typically.n-Si

i-Sip-Si《集成平面光波導(dǎo)器件》課程58

The

optimization

of

“classical”

modulators

relies

on

the

optimization

of

the

overlap

between

the

optical

mode

and

the

depletedwaveguide

is

usually

much

smaller

than

the

modal

sizeFrom

the

idea

to

the

final

deviceOptimizationFigures

of

meriteSimulation

of

the

diode

CouplersOptimized

structure

10G

40G

Frequency

and

data

transmission《集成平面光波導(dǎo)器件》課程59TechnologyLayoutCharacterization(μm)

y

neffx

(μm)PIPIN

diode

principle

PIPIN

diodeActive

region8X10-42.0x10-4

Metal

Metal

P‐doped

region

N‐doped

region

Optimization

of

the

overlap

between

the

optical

mode

and

the

depleted

region.

Low

insertion

loss

2x101740,90,710,9

1.50,7-1V0

-5

-4

-3

-2Hole

concentration

variation3

1.00,50320,500.55410.0

20Refractive

Effective

variation

variationindex

index《集成平面光波導(dǎo)器件》課程

2,5x

(μm)2,5

3

Voltage

(V)60evel

(/cm3)

Doping

leSelf-aligned

fabrication

processDepth

(μm)《集成平面光波導(dǎo)器件》課程61RESISTInAll

silicon

carrier

depletionmodulator

OutModulator

lengths:

0.95

mm

and

4.7

mm《集成平面光波導(dǎo)器件》課程62RF

characteristics40Gbit/sL

=

4.7

mmExtinction

ratio:

6.6

dBInsertion

loss:

6

dB

《集成平面光波導(dǎo)器件》課程63Ring

resonator

modulators

PIPIN

diodeRing

radius:

50μmTETM10Gbit/sExtinction

ratio:

4-5

dBInsertion

loss:

~1dB《集成平面光波導(dǎo)器件》課程64DiodeV

L

Activeregionglength40Gbit/sEROn-chipIL(maximum(transmission)Opticallossat40Gbit/soperat.pointverticalpn[Intel]4V.cm1mm1dB4dB-lateralpn[Univ.Surrey]2.7V.cm3.5mm10dB15dB15dBMaincharalateralpn[Univ.Surrey]2.7V.cm

P1mmtobe3.5dB(improved:5dB35dBPowerlateralpn[Univ.Surrey]2.7V.cm

1mmti7dBJ/bit)5dB8dBVoltawrappedaroundpn14VV.cm[Univ.Surrey]geswing1.313mm(>5V)6.565dB15dB25dBpipin[Univ.ParisSud]3.5V.cm4.7mm6.6dB6dB6dBpipin[Univ.ParisSud]3.5V.cm0.95mm3.2dB4.5dB4.5dBState

of

the

art《集成平面光波導(dǎo)器件》課程65Power

consumption

evolution

Carrier

depletion

mo