Semiconductor devices and opto-electronics

Meint Smit

Leon Kaufmann

Xaveer Leijtens

Opto-Electronic Devices GroupEindhoven University of Technology

2

Course information

• Opto-electronics:– Book: Gerd Keiser, Optical Fiber Communications

3rd edition, McGraw-Hill, obligatory!– Contact: Xaveer Leijtens

x.j.m.leijtens@tue.nl040 – 247 5112

• Electronic devices:– Book: Linda Edwards-Shea, The Essence of Solid-

State Electronics, Prentice Hall, obligatory!– Contact: Leon Kaufmann

l.m.f.kaufmann@tue.nl040 – 247 5801

• Website: http://oed.ele.tue.nl (education)

3

Course overview

Week Mon 1,2 Tue 1,2 Wed 2,3 Fri 2 (vko) Fri 3,4

49 Lect o Lect e Instr o Lect e Lect o

50 Lect e Instr e Instr o Lect e Lect o

51 Lect e Instr e Instr o Lect e Lect o

2 Lect e Instr e Instr o Lect e Lect o

3 Lect e Instr e Instr o Lect e Instr e

4

Contents semiconductor devices

• Recapitulation: electrons in atoms, introduction to quantum mechanics

• Solid state materials: crystal structures, energy band diagrams of insulators, metals and (un)doped semiconductors

• Semiconductors and carrier transport• Principle of operation of pn junction diodes• Fundamentals of MOSFETs• CMOS technology (incl. video demonstration)

5

OGO3.2Free space optical communication

Kickoff Meeting Dec 1 in MA1.41 13:30h

6

Contents Opto-Electronics

Lecture Chapter About

1 1 Introduction

2 Optical fibers

2 3 Fiber transmission properties

5 Power launching and coupling

3 4 Light sources

4 6 Light detectors

5 7 Optical receivers + guest lecture

7

Examination

• Closed-book examination, formula sheet will be provided• Electronic devices: Edwards-Shea, chapter 1-8• Opto-electronics: Keiser

Chapter # pages

1 not: 1.4 and 1.5 15

2 not: 2.3.5, 2.4.3-9, 2.7.2-4, 2.8-10 30

3 3.1.2-3.1.4: no formula’s, only mechanismsnot: 3.1.5, 3.3, 3.4, 3.5.4-5

28

4 not: 4.4 and 4.5 44

5 not: 5.1.3, 5.2.1-end, with p 212, 218 8

6

7

8

Optical communication

+ ––

TRANSMITTER FIBRE

+ –

RECEIVER

9

Electromagnetic spectrum

• Optical communication wavelength: = 1500 nmcorresponds to = c/ 200 THz = 200.000 GHz

• 1% = 2 THz = 2000 GHz• EDFA-bandwidth 30 nm 4 THz

10

Standard Single-Mode (SM) Fiber

Fiber coreSiO2+ GeO2

Ø 10 mn 1.443

SiO2 Cladding

Ø 125 mn 1.44

Primary coating (soft)Ø 400 m

Secondary coating (hard)Ø 1 mm

11

Optical source

+ ––

TRANSMITTER

FIBER

Performance

Modulation speedFiber-coupled power

12

–

Light Emitting Diode (LED)

Typical performance data

Power in MM-fiber: 100 W

Power in SM-fiber: 1 W

Direct Modulation Bandwidth: 100 MHz

+

13

Laser

Typical performance

Power (in fiber): 5-10 mWMax: 100-300 mWDirect Modulation Bandwidth: 1-10 GHz

14

Photodiode detector

Typical performance data

Responsivity: ~1 mA / mWBandwidth: 1-20 GHz

+ –

15

Optical communication systems

First Generation, ~1975, 0.8 mMM-fiber, GaAs-laser or LED

Second Generation, ~1980, 1.3 m, MM & SM-fiberInGaAsP FP-laser or LED

Third Generation, ~1985, 1.55 m, SM-fiberInGaAsP DFB-laser, ~ 1990 Optical amplifiers

Fourth Generation, 1996, 1.55 mWDM-systems

1.80.8 1.0 1.2 1.4 1.60.9 1.1 1.3 1.5 1.7Wavelength (m)

Att

en

ua

tion

2 dB/cm

16

WDM-transmission

MultiwavelengthTransmitter

MUX

MultiwavelengthReceiver

DMX

opticaltransmitter

opticalreceiver

optical fiber

+ –

17

Erbium-Doped Fiber Amplifier (EDFA)

PUMP LASER 0.98 m or 1.48 m

Er-doped fiber

MUX FILTER

-10

0

10

20

30

1520 1530 1540 1550 1560 1570

wavelength (nm)

ED

FA

ga

in (

dB

)

18

Synchronous Digital Hierarchy

Data rate SDH

Europe

SONET

US & Japan

52 Mb/s OC-1

155 Mb/s STM-1 OC-3

622 Mb/s STM-4 OC-12

2.5 Gb/s STM-16 OC-48

10 Gb/s STM-64 OC-192

40 Gb/s STM-256 OC-768

EuropeSDH: Synchronous

Digital Hierarchy

STM: SynchronousTransport Module

US & JapanSONET: Synchronous

Optical Network

OC: OpticalCarriers

19

WDM experiments

Si electronics

ETDM

installed(10x / 6 yrs)

(10x / 2.5 yrs)

5 yrs

0.01

0.1

1

10

100

1000

10000

1980 1985 1990 1995 2000

Cap

acit

y (G

b/s

)

Trunk transmission capacity

20

# W

DM

-cha

nnel

s

4

16

64

256

0.01 0.1 1 10 100

Channel bitrate (Gb/s)

1

Trunk transmission capacity

•‘97

10 Gb/s

1 Tb/s

0.1 Gb/s

1 Gb/s

100 Gb/s

•‘98

•‘98•

‘99

•‘00

•‘04?

•‘86

•‘96

•‘89

•‘83

•‘80

21

Undersea cables

22

Undersea cable

Cable Capacity fully upgraded (Gbps)

2,400

Fiber Pairs 6

Wavelengths per Fiber Pair 40

Gbps per Wavelength 10

Cable Length (km) 14,500

23

Optical Transport Network

Global Network

Wide Area Network

Metropolitan/Regional Area Optical Network

Corporate/Enterprise Clients

Cable modemNetworks

Client/Access Networks

FTTHMobile

SDH/SONET

ATM

PSTN/IP

ISPGigabit Ethernet

Cable

FTTB

ATM

< 10000 km< 10 Tbit/s

< 100 km< 1 Tbit/s

< 20 km100M - 10 Gbit/s

Courtesy: A.M.J. Koonen

24

O X C

1

2

1

2

in out

X

X

X

X

Integrated optical cross-connect

Dimensions: 8x12 mm2

25

Fibre propagation

n1

n2

26

Fiber performance

z=0 z=L

Dispersion

z=0 z=L

Attenuation

27

Optical attenuation in glass

1960

Att

enua

tion

(dB

/km

)

1

10

100

1000

0.11970 1980 1990 2000

20 dB/km (Corning)

0.16 dB/km

CVD (Chemical Vapor Deposition)

28

1.80.8 1.0 1.2 1.4 1.60.9 1.1 1.3 1.5 1.7

Wavelength (m)

Att

enua

tion

(dB

/km

)

0.2

0.5

1.0

1.5

0.16 dB/km

Rayleighscattering

IR band edge

OH--peak

UVabsorption

0.70.6

Fiber attenuation (SiO2)

29

A note on dB and dBm

• dB– optical signals:

– electrical signals:

–

• dBm– absolute power value (with 1 mW as reference)

– power level in dBm:

2

1log10P

P

22

11

2

1

2

1 log10log20log20IV

IV

I

I

V

V

mW

P

1log10

elelopt PIP electrical dB = 2 x optical dB

30

Reflection & refraction

n2<n1

n1

1 1

1

2

2

Snell’s law

2211 sinsin nn

2211 coscos nn

n2<n1

n1

1= c

c

Critical angle

1

2sinn

nc

1

2cosn

nc

n2<n1

n1

1 >c

Total internal reflection

31

Numerical Aperture

1

2cosn

nc Critical angle:

Maximum entrance angle:

cn

n sinsin0

1max,0

Multimode fiber

n1

n2

0

c

n0

n0

22

21

211max,00 cos1sinsin nnnnnNA cc

Numerical aperture:

n

n

n

nn

n

nn

nnn

1

212

1

22

21

21

2

: if 222

22

1 nnnnnNA

61.0 max,0NA

32

L

n1

n2

Dispersion (intermodal)

c

t

c

n

n

nL

T

2

1

c

nLT 1

min

cc

nLT

cos1

max

1

2cosn

nc

c

n

c

n

n

nL

T

2

1

nc

NA

c

n

c

n

n

nL

T2

2

2

1

T

LLB

2

2

NA

nc

T

LLB

kmnsnc

NA

c

n

c

n

n

nL

T /2

2

2

1

kmsMbNA

nc

T

LLB )/(

22

33

Bandwidth and bit rate

tT

FWHM

dBo

0

1.5

3

oe

dBe

0

3

6

oe

e

CCT

B

22

1120

Rule of thumb:

(incoherent)

Bandwidth

Cross talk

opteldet PPI

34

refractiveindex

SM Single-Mode

Fiber types

MM-SIMulti-ModeStep Index

MM-GIMulti-ModeGraded Index

2/1

1 21

a

rnrn

35

Fiber classification (1)

Core diameter 50 - 400 m

Cladding 125 (500) m

2nd coating 250 - 1000 m

NA 0.16 - 0.5

Attenuation 1 - 4 dB/km

Bandwidth 6 - 25 MHz.km

Application Short distance, low cost

limited bandwidth

MM-SI: Multi Mode - Step Index fiber

36

Fiber classification (2)

Core diameter 50 m standard

Cladding 125 m

2nd coating 200-1000 m

NA 0.2 - 0.3

Attenuation 1 dB/km (1300 nm)

Bandwidth 150 MHz.km - 2 GHz.km

Application Medium distance communication

LED/Laser sources

MM-GI: Multi Mode - Graded Index fiber

37

Fiber classification (3)

Core diameter 3-10 m

Cladding 50-125 m

2nd coating 200-1000 m

NA ~0.1 (not used)

Attenuation 0.20@1550 - 0.4@1300 dB/km

Bandwidth >> 500 MHz.km

Application Long distance communication

Lasers, standard fiber

SM-SI: Single Mode - Step Index fiber

38

The wave equation

Plane wave:

Spherical wave:rjkeE

R

eE

Rjk

Solutions to Maxwell’s equations:

2

kn

knk

/0

0

r

rr

n

kk

0000

phase fronts

39

Wave vector and decomposition

kz

kx

kkx

kz

z

x

z

x

zjkxjk zx eezxE ),(

zz

xx

k

k

2

2

40

Interference

x

x

z

z

phase frontsabsorber

metallic plates

kz

kx

k+

kx+

kz

+

kx-

k-

-

zjkx

zjkxjkxjk

rkjrkj

z

zxx

exk

eee

eezxE

cos2

,

xx

xz

k

nkk

kkk

2

0

22

41

The metallic waveguide

metallic plates

d

z

x

kz zj

x exkzxE cos,

dx 2x

xk 2

220

2xz kknk

42

Modes & Rays

waveguide

d

2 1 0

m=0 m=2m=1

d

mk mx

1,

0

,arcsinnk

k mxm

43

Optical waveguide modes

m=0 m=4m=3m=2m=1

n2

n1

n0

k

z

m=0m=1

m=2m=3

m=4

kx

n1k0

c2

c0

substrate modes

superstrate modes

guided modes

n0k0n2k0 n1k0

44

Mode intensity profiles

• Optical modes:

• Excitation of modes:

0 1 2

d

a

Planar:

Single-mode if V

Fiber:

Single-mode if V 2.405

22

21

2nn

dV

22

21

2nn

aV

45

V-parameter

• V number: determines how many modes a fiber supports

• Lowest order mode HE11 has no cut-off

• Single-mode fiber:

NAa

nna

V

22 2

22

1

405.2V

46

Number of modes

• Number of modes in step-index fiber

• Optical power in the cladding

2

2

2

1 22

22

1

2V

nna

M

MP

Pcladding3

4 for large values of V

47

Step index fiber modes (2)

Effective index /k as a function of

Single-mode fiber: V 2.405

NAa

nna

V

22 2/12

22

1

HE11

TE01TM01

EH11

HE12

HE31

0 1 2 4 53 6

n1

n2

k

48

Birefringence

• HE11:

• Birefringence: difference in effective refractive indices between two polarization modes

• Fiber beat length: phase difference between the two polarization modes is

xyf nnB

xyp nnk

L

0

Horizontal modeVertical mode

49

Fiber materials

• Silica glass fiber– starting material: pure silica (SiO2) in the form of fused quartz

(amorphous)– modification of refractive index by addition of impurities

• lowering refractive index : B2O3, F• raising refractive index : P2O5, GeO2

• Polymer optical fiber (POF)– large core (multimode)– large refractive index difference between core and cladding– easy handling– relatively high losses

50

Losses in polymer optical fiber

• Absorption loss in POF >>> Absorption loss in Silica fiber search for low loss polymers

• PMMA (Poly Methyl Metacrylate)• PS (Polystyrene)• FA (Fluoro acrylate)

– Typical absorption levels: 100 dB/km– Low loss windows: several windows in the range 500-800 nm

• New material development: perfluorinated polymer 50 dB/km from visible to 1600 nm

• Core type• Step index• Graded index

51

Advantages of Optical communication

Huge bandwidth

Small and light

Low loss

Electrical isolation

No EMI (Lightning, interference)

Security (no tapping)

Reliability

Low cost per bit