Pump Diode Lasers: Applications and Technology

Pump Diode Lasers:Applications and Technology

Christoph Harder, Harder&[email protected]

Photonics 2008, Dehli2008 12 13

112/11/2008 Photonics 2008, Dehli

Pump Diode Lasers

1. Photonic Market– Global Photonic Market– High Power Diode Laser Applications– Photonic Manufacturing

2. Applications– Photonic Tools– Power Photonics

3. Narrow Stripe Pump Diode Lasers– Single Mode Devices

4. Broad Area Pump Diode Lasers– Multimode Devices– Optical coupling to fiber– Heat removal

5. Status, Trends, Opportunities– VCSEL


Acknowlegement

• OIDA, Michale Lebby• OITDA• EPIC, Tom Pearsall• Bookham: Boris Sverdlov, Nobert Lichtenstein, Susanne Pawlik, Gunnar Stolze, Dominik Jäggi• Intense: John Marsh, Iulian Petrescu-Prahova, Chris Baker, Stewart McDougal, Steve

Gorton, Berthold Schmidt• ILT Aachen: Reinhart Poprawe• JDS Uniphase: Toby Strite, Victor Rossin, Erik Zucker• Trumpf: Friedhelm Dorsch• Trumpf: Friedhelm Dorsch• ETH Zürich: Bernd Witzigmann• Fraunhofer Institut USA – Visotek: Stefan Heinemann• Coherent: David Roh• Laserline: Volker Krause• Newport Spectra: Ed Wolak, Jim Harrison, Michael Atchely• IPG: Alex Ovtchinnikov

Based on Seminar by Berthold Schmidt: “High Power Laser Diodes: Technology and Applications”applications of High Power Semiconductor Lasers, San Diego, California, Oct 6, 2008

Reference: Optical Fiber Telecommunications, Academic Press, A: Components and SubsystemsISBN: 978-0-12-374171-4, chapter 5 “Pump Diode Lasers” by Ch. Harder


Global Photonic Market


Opportunities – The MarketWorld Market 2005 (production)

Photonics World Market by Sector, 2005

Optical

components &systems

6%

Measurement &automated vision

8%

Defence photonics8%

Productiontechnology

6%

Total: EUR 228 Billion

EPIC, The European Photonics Industry Consortium Activities and Markets in Europe

5

6% 8%8%

Medical techn. &life science

8%

Opticalcommunications

5%

Information

technology21%

Lighting8%

Solar energy4%

Flat panel displays26%

OPTECH CONSULTING - October 2007

Opportunities – The MarketWorld Production by country

World Production Volume by Country, 2005

Total: EUR 228 Billion

The Netherlands2%

Japan

32%

Europe Other

4%


6

France

2%

Germany

7%

Italy

2%

UK

2%

Other (incl. China)

11%North America

15%

Korea

12%

Taiwan

11%

Europe total: 19%OPTECH CONSULTING - October 2007

Projected Market Growth till 2015

7

• Laser diode market in the range of only 1-2% of the overall photonics market

• Biggest Diode Share: Telecom, optical storage (75-90%)

• Gray areas: Value of material processing (system level), defense budget

AHPSL 2008 Seminar #1

Global Photonic Market: Japan


Domestic ProductionDomestic Production -- OE vs. ElectronicsOE vs. Electronics

4.92.5

2.4 1.0 ▲1.9

28.9

11.2

▲15.1

2.7

19.92.4

4.34.0

▲0.3

2.1

6.4

兆円

)

対前年度成長率

5

6

7

8

9

10

Optoelectronic Products

Tri

llio

nJP

Y

4.9

▲0.7

0.3

▲12.0 ▲5.6

2.34.6 6.6

6.1

▲10.5

0.59.6

▲18.2▲12.0

7.0

11.49.1

4.39.1 4.0

20.5

2.3

▲3.5

1.86.5 3.1

生産金額

(兆円

0

1

2

3

4

5

Estimate

91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08Prospect

Electronics Products (x 1/10)

Tri

llio

nJP

Y

Year

2

3

4

Display

Input / Output Equipment

trillio

nJ

PY

trillio

nJ

PY

Domestic OE Products Trends by FieldDomestic OE Products Trends by Field

Fiscal Year

0

1

91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08

Optical Storage

Optical Communication

Laser Processing

Sensing/Measuring

Photovoltaic Cells

trillio

nJ

PY

trillio

nJ

PY

Estimate Prospect

Global Photonic Market: USA


OIDA is broadening optoelectronics with“Green photonics” opportunities

Value Chain

Service

Providers

Systems

Green - Eco-System “Ecomation”Green photonics systems and components

Home display, solar cell, lighting windows/panels

TelecomSystems

TelecomCarriers

Opportunities Active Presence

Wireline/wireless carriers; Lighting architects;Consumer services; media/content providers

OIDA: Optoelectronics Industry Development Association

Technology Breadth

Modules

Components

Sources: OIDA

Telecommodules

TelecomDevices

SensingIndustrialDevices

MilitarySpec

Devices

Medical &High power

lasers

LightingModules

AdvancedMaterials

Nano/BioPackages

SensingIndustrialModules

LightingDevices

Solar &EnergyDevices

DisplayDevices

Solar &Energy

Modules

DefenseSecurityModules

High Powerlaser

modules

Common platforms for Green photonics…

Diode laser revenues by application

Diode laser revenues by segment

3500000

4000000

4500000

Diode Pump Lasers

Other

Optical storage will continue to suffer margin erosion

Diode pump lasers grow 62.8% in 2006 over 2005

Michael Lebby ([email protected])

Where is the new cash cow?

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

2005 2006 2007 2008

Re

ve

nu

es

($k

)

Sensing

Barcode Scanning

Inspection, Measurement, Control

Image Recording

Entertainment

Optical Storage

Telecom

Basic Research

Instrumentation

Medical

Materials Processing

Sources: OIDA, OIDA members, Laser Focus, OIDA consultants

Global Photonic Market: Europe


European Production in a Global Context


15

Production technology

Optical communication

HPL Applications at a glance

• material processing, analysis, measurement

• Data transmission, Optical amplification

• Communication (inter satellite,..), distanceDefence & Aerospace

Information Technology

Medical

• Communication (inter satellite,..), distancemeasurement, countermeasure,target designation, Illumination, LIDAR,...

• Optical storage, printing, marking, display

• Aesthetics (Skin treatment,..), surgery,therapy (PDD -Photodynamic disinfection-,PDT -therapy-,..), ophthalmology, Cancertreatment

16 AHPSL 2008 Seminar #1

High Power Diode Laser Applications:Information Technologies


4.7 GB700 MB

NA

25 GB

Wavelength 780 nm

0.45 0.60 0.85

Capacity

CD DVD

4.7 GB (1 layer)

0.6

mm

1.2

mm

700 MB

NA

0.1

mm

25 GB (1 layer)

Wavelength 780 nm 650 nm 405 nm

0.45 0.60 0.85

Capacity

CD DVD BD

Progress of Optical StorageProgress of Optical Storage

Label surface Label surface Label surface

8.5 GB (2 layers) 50 GB (2 layers)

Blu-rayDisc

Blu-rayDisc

0.6

mm

1.2

mm

0.1

mm

Blu-rayDisc

Blu-rayDisc

Track pitch 1.6 μm 0.74 μm 0.32 μm

High Power Diode Laser Applications:Communication Technologies


Worldwide laser diode market history from 1996

6000

7000

Diode lasers will struggle to grow revenue

Telecom experiencing margin erosion

Optical storage squeezed out by flash

Michael Lebby ([email protected])

0

1000

2000

3000

4000

5000

6000

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Reven

ue

($k) Other

Optical Storage

Telecom

total

Telecom and storage entering maturity?

Sources: OIDA, OIDA members, Laser Focus, OIDA consultants

IBM Research Laboratory:980 Diode Laser

Disruptive Technology: Magic Fiber: Erbium doped fiber

21

Today:

A few hundred channels at 10Gb/sover a few thousand km!

Optical Amplifier:

as power supply

We were the only laser supplier forhigh power and high reliability


Why High Power 980nm Pumps?

Input

DispersionCompensating

Fiber

Coupler

Isolator & filter

ErbiumDoped Fiber

GainFlattening

Filter

Coupler Isolator

Output

ErbiumDoped Fiber

ErbiumDoped Fiber

Typical 3-stage EDFA

www.bookham.com Page 22

1480 Pumps (now 980nm !):• Advantage:

• higher optical conversion efficiency

• Disadvantage• Increased noise figure• More expensive coupler• High heat load, expensive cooling

980 Pumps:• Advantage:

• Low noise figure (3 level)• Low heat load• High laser efficiency• Low cost coupler• Un-cooled operation

•Disadvantage• Lower optical powerconversion efficiency High power 980 pumps enable low cost EDFAs


High Power Diode Laser Applications:Production Technologies


Domestic Output of Laser ProcessingDomestic Output of Laser Processing

300

400

500

600

Oscillators

Other Laser Processing Equipment

Eximer Laser Material Processing

Do

mesti

cP

rod

ucti

on（

bil

lio

nY

en）

0

100

200

300

03 04 05 06 07 08

Eximer Laser Material Processing

Solid-State Laser Material Processing

CO2 Laser Material Processing

Medical Laser Equipment

Fiscal YearEstimate Prospect

Do

mesti

cP

rod

ucti

on

Electronics

Light weight structuresAutomotive

Sheet Metal

102

100

10-2

Drilling

EngravingTuningMarkingMicro joining

Cutting

Welding

Semi finishedProducts

Micro welding

Forming

Surface Technology

FunctionalSurfaces

Typ

ical

Dim

en

sio

n[m

]

Ship Building

Remote

Hybrid

SelectiveLaserMelting

Production Technologies:Geometric scaling of material processing

EUV/13nm

Computer chips

ElectronicsMicroelectronics

Electronics

1970 1980 1990 2000 2010Year

10-4

10-6

10-8

HardMaterials

Micro joining Surfaces

Micro processing

CommunicationData Processing

Optical Memories

OptoelectronicsMicro Lithography

Typ

ical

Dim

en

sio

n[m

]

Melting

Polishing

Bio-photonicsLIBS

Which Laser for which Application?

Source: Prof. Dr. Reinhart Poprawe, ILT (AKL 2008)


Production Technologies:Welding


Developing trends for Lasersand their applications

Beam

Para

mete

rP

roductB

PP

[mm

mra

d]

10

100

1.000

plasticswelding

solderingselective

laser powderremelting

transformationhardening

melting,cleaning

brazing

F#4 focusingoptics (NA 0,12)

metalsheet

deep penetrationwelding metals

2008

f

2w0

2003

Diode lasers(2003)

AL-welding (DDL system)

BPP = q · w0

Laser Power P [W]

Beam

Para

mete

rP

roductB

PP

[mm

mra

d]

1 10 100 1.000 10.0000.1

1

10

Printingtherm. marking

sheetcutting

CO2-laser

DPSSL

lamp pumpedNd:YAG-laser



Foils-Polypropylen (PP)transparent and blackthickness 100 µm

Microfluidic device- PMMA or PP sealing

Application example: welding of thin foils

- PMMA or PP sealingfoil (75 µm)

P= 1,4 – 5,9 Wv= 50 to 250 mm/sd0= 70 µmdweld seam= 150 to 500 µm



Double sided butt joint 30kW

2” stainless steel

P=20 kW, v= 0,8 m/min

18 11/10/2008 IPG Photonics Confidential

P=30 kW, v= 2,0 m/min

Single Mode Welding

Power: 3kWStainless Steel

v=0.5m/minDepth=1 3mmWidth≈1mm


v=10m/minDepth=6mmWidth≈0.2mm !!!

Source:


Thick Section Welding YLR20000

2 inch =50.8 mm

10 11/10/2008 IPG Photonics Confidential10 11/10/2008 IPG Photonics Confidential

Butt joint 2 inches (50.8 mm)Double sided weldingStainless steel 1.4301

Overlap joint 2x 15 mmStainless steel 1.4301

Thick Sheet Welding

-Tube fabrication (5 – 20 mm)

-Pipeline Welding (10 – 20 mm)

-Power plants (up to more the 50 mm)

-Chemical reactors

-Shipbuilding and Offshore technology


Laser-HybridLaser X70

t = 12 mm

PL = 10.5 kWvS = 2.2 m/min

Scanner und KUKA RoboScan - Scanner and KUKA RoboScan

Bewertungskriterien:Versatzgeschwindigkeit - Schweißgeschwindigkeit - Taktzeit - Linienkonzept - Komponentenflexibilität - Arbeitsabstand - fixe und

variable Kosten - Zugänglichkeit - Nahtgeometrie - Bauteilflexibilität - Lasernutzung - Schweißqualität

RoboScan - ZoomoptikKUKA Systems GmbH | Prozesstechnik | Dr. Rippl | 05.11.2008 | Seite 3 www.kuka-systems.com


Assessment criteria:cross velocity - welding speed - cycle time - line concepts - flexibility of components - working distance - fix and variable costs -

accessibility - seam geometry options - part flexibility - efficiency of laser source usage - weld quality

Production Technologies:Surface Finish


Materials: 1.2343, 1.2344, 1.2316

Initial state:milled, eroded,grinded

1 mm

Sharp edgemaintained

2002 2008

Application example: laser polishing

Results:from Ra = 1 - 3 µmto Ra = 0,09 - 0,3 µm

Processing time:1 - 3 min/cm²

polished by Laser (Ra=0,24µm)

milled (Ra=1,7µm)

1 mm10

µm

2002 2008Ra = 0,35 µm Ra = 0,09 µm



Information technology:optical storage, printing, display

CTP Printing - Computer to plate (CTP)Printing

- Digital printing

- Display (RGB) technology

- Rear projection TV


Production Technologies:Rapid Prototyping


Application Example SLM of ZrO2-based Ceramics

• Zirconium oxide (ZrO2):max. bending strength,resistance to wear andtensile strength

• Principle of SelectiveLaser Melting (SLM):Ceramic powder is fullymolten (no sintering)molten (no sintering)

• Potential Application:Production of full-ceramicdental prostheses

10 mm

SLM demo parts



Production Technologies:Cutting


CO2


Medical applications:

Ophtalmology

Hair removal

- Acne treatment

- Photodynamic Therapy (PDT)

- Photodynamic Disinfection(PDD)

- Dental

Before After

Skin Treatment: Tattoo / Hair Removal

Surgery Before After


Laser countermeasure systemagainst heat-seeking missilesExample: Directional Infrared Countermeasure

Defence and homeland security applications:slowly evolving

Distance measurement,Example: Directional Infrared Countermeasure(DIRCM) from Northrop Grumman (publicInformation)

Laser area defence system(LADS from Raytheon)(public Information)

Distance measurement,

Target designation

- Laser fuses

- Illumination

- Detection of chemicals


Photonic Tools:


600

800

1.000

1.200

1.400T

ota

lT

urn

Aro

un

d World Market 2007

Extrapolation of currenttrends to 2010

Including new

Laser Market Development by Laser Type

0

200

400

600

CO2

LPYAG

DP

YAGFi

ber

HPDL

Excim

er

Laser Type

To

talT

urn

Aro

un

d

Including newapplications / markets2010



Photonic Tools:Overview


Laser system design principles

t ransversallypumpedrodlaser

INNOSLAB laser

f ibre laserend-pumped

All based on the samedesign principle requiring

• Mirrors (Cavity)

• Gain medium


thindisk laser

f ibre laser“ Y” -pumped

46

• Gain medium

• Pump source

Extension...amplifier technology


Photonic Tools:Disk Laser


1

End-mirror

Disk

Bending prisma

Parabolic Mirror

Pump- Beam

1

Pumping of a Disk

48

Disk

Cavity

1

2

34

5

8

6

7

Outcoupler

Laser beam

1

Actually: 20 passes of the pump light through the disk!


12/11/2008Photonics 2008, Dehli

Design of a disklaser (8 kW)

ResonatorResonator

49



Disklaser: TruDisk

50

TruDisk 1000 TruDisk 8002



> 5 kW Output Power per Disk

4000

5000

6000

Ou

tpu

tP

ow

er

PL

(W)

40

50

60

70

op

t.E

ffe

icie

nc

yη

op

t.-o

pt.

(%)

51

0

1000

2000

3000

0 2000 4000 6000 8000

Ou

tpu

tP

ow

er

Pump Power Pp (W)

0

10

20

30

40

op

t.E

ffe

icie

nc

y



TruDisk 10003 – 4 disk resonator

8000

10000

12000

14000

40%

50%

60%

70%O

utp

ut

Po

we

rP

L[W

]

Op

tic

ale

ffic

ien

cy

op

t.-o

pt.

52

0

2000

4000

6000

8000

0 5000 10000 15000 20000

0%

10%

20%

30%

40%

Ou

tpu

tP

ow

er

P

Op

tic

ale

ffic

ien

cy

Pump Power Pp [W]12/11/2008Photonics 2008, Dehli

Power Photonics


Fiber combinerFused and Proximity

Fused: (6+1)*1 Proximity: (2+1)*1

Fused can be extended to beyond 20 inputs

Proximity needs high brightness pumps

Fiber NA

Signal input HI 1060

Pump Ports 6*105um 0.22

Output 20um/400um 0.06/0.46


Yb fiber wavelength: 9xx bands

Yb: Glass fiber absorption and emission spectrum

Wide pump band: 870nm to 980nm

Blue band (915nm): Good absorption, wideband– Preferred for lower power, high gain stage

Green band (940nm..960nm): Lowest absorption, wideband, high optical conversion– Preferred for very high power stage

Red band (976nm): Highest absorption, narrow width– Preferred for high gain amplifiers and q-switched lasers with short fiber (SBS)– Pump diode challenge: Diode wavelength control (+/-2nm) necessary


Fiber Laser: MOPA

Seed laser

Pump Diode

Dual Clad Yb

MMPMFPMF

• Seed laser– Fiber laser: Good spectral control

Need external modulators (Pockels Cell)– Diode laser: Excellent dynamic control

FP laser have poor spectral control, of no concern DFB have excellent spectral and dynamic control

• Pumplaser– Single emitter broad area MM diode

Seed laserPump Diode


Photonic Tools:Fiber Laser


directly modulated

Laser Diode

SPI G3 Yb doped Pulsed Fibre Laser 1 064nm wavelength

MOPA (Master Oscillator Power Amplifier) architecture

Yb fiber laser

Amplifier Chain(GTWave Technology)

SeedLaser

Average Power: 20W Spot size: 40um with x3 Beam Expander, 9mm input beam diameter

Pulse width: 10-70ns FWHM

Peak Power: 14kW per pulse Power density: up to 1GW/cm2 for 40um spot size

Pulse Energy: 0.8mJ max

Pulse frequency: up to 500KHz, 25 preset pulse waveforms

Pre-Amp Post-Amp

Status and Development of Single ModeFiber Lasers

Comerical SM-Lasers

10000W(under development)

12000

10000

8000


100W 500W50W35W

1000W

3W 10W 20W

5000W

3000W2000W

0

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

6000

4000

2000

Release

High Power Fiber Lasers - History

Power development of Low Order Mode Fiber Lasers

60000

50000

40000

30000

50.000W

36.000W


2001 2002 2003 2004 2005 2006 2007 2008 2009

Introduction in Industrial Market

30000

20000

10000

0

17.000W

7.000W

700W 4.000W

Aktivitäten im FüLas-Projekt - FüLas project activities

100µm

Laserleistung 8 kWBPP ~ 4.5 mm*mrad

200 µm

BS

A


RoboScan - ZoomoptikKUKASystems GmbH | Prozesstechnik | Dr. Rippl | 05.11.2008 | Seite 8 www.kuka-systems.com

Laser power 8 kWBPP ~ 4.5 mm*mrad

Large distance between laserand beam switch respectively

production cell

Große Abstände zwischenLaser und Strahlweiche bzw.

Bearbeitungszelle

A

200 µm

BPP ~ 8 mm*mrad

B

Single Mode

• Single Mode Fiber Pump Module• Pump Diode Beam• Pump Diode Beam: Slow axis• Ridge waveguide• Shift Kink• Vertical epitaxial structure• Length Scaling• Length Scaling• Spectral stabilization• Passivation• Packaging• Reliability

• Literature

12/11/2008 62Photonics 2008, Dehli

Majority of diode based laser systemshave common design requirements:

• Efficient coupling into

passive optics elements or

an optical fiber (with low NA)

System Design Requirements

• High wall plug efficiency (low power consumption)

• Good system reliability

• Cost competitive

• Simple to use (cooling, turn on time, robustness,…)

From a diode perspective this relates to various designobjectives….


Common design requirements for high power laser(HPL) diodes:

• High output power

• High brightness

Laser diode design targets

• High brightness

• High wall-plug and coupling efficiency(low power consumption)

• High reliability + robust

• Design capable for high volume manufacturing


Single Mode Fiber Pump Module

• 600 mW Power at 1 A operating current• Wavelength locked by FBG over 70 K with high side lobe suppression ratio


Single Mode Fiber Pump Module

• Fully monolithic planar AlN substrate– Extremely low mechanical creep– Cost effective automation– Excellent thermal properties

• Used in Butterfly packages and coolerless MiniDIL– i.e. 400 mW Submarine MiniDIL, 600mW Butterfly

12/11/2008 Page 66Photonics 2008, Dehli

BFM

Thermistor

Laser

Carrier

Fiberfixing

Pump Diode Beam

Single Mode Fiber: NA=0.12

1 um 4 um

Laser Diode:

– In slow axis: NA=0.12, matched to NAof fiber

– In fast axis: NA=0.5, polish lens onfiber tip

Coupling

– At distance of 4um: Profiles matchProf. Unlü, Boston

0 um


Pump Diode Beam

Single Mode Fiber: NA=0.12

CW operationT = 25 °C

~ 1200 mW

~ 900 mW

~ 600 mW

~ 1200 mW

~ 900 mW

~ 600 mW~ 7.5° ~ 19°

lateral far-field vertical far-field

NA=0.12

Coupling: NA matching

– Laser diode in slow axis:NA=0.12, matched to NA of fiber

– Laser diode in fast axis: NA=0.5,polish lens on fiber tip

Coupling: Amplitude matching

– At distance of 4um: Profilesmatch

NA=sin(angle)~angle

Slow axis: NA=0.12 ~7deg

Fast axis: NA=0.5~30deg

angle (°)

-40 -20 0 20 40

~ 300 mW

-20 -10 0 10 20

~ 300 mW

angle (°)

NA=0.5


Pump Diode Beam: Slow axis

Pump Diode is dielectric waveguide- Low loss through total internal reflection- Can be decomposed in slow axis and fast axis- Each a dielectric slab waveguide with

dn=1/2*(NA/n)2

For NA=0.12 and n=3.6 ->dn=5*10-4


∆=dn=n1-n2

Pump Diode Beam: Slow axis

For slow axis: Need waveguide with small dn=5*10-4 n

How can this be achieved?By weak waveguide such as

n2 n1 n2 n2 n1 n2

Ridge Waveguide Disordered waveguide


dn=n1-n2

Pump Diode Beam: Slow axisEffective Index approach

dn=n1-n2

n2 n1 n2

n2 n1 n2

• Effective Index approach– Calculate effective index of

planar waveguides (centerand outside)


n1 n2

Ridge waveguide

• Ridge Waveguide

– One growth step, simple process• Built in reliability

• InGaAlAs for best material properties

– Confinement• Index guided mode: High linear power and excellent coupling

to fiber

• Temperature insensitive current confinement

– Scalability• Increase power by making chip longer


‘Shift’ Kink: Observation

• Observation (1991)– Sudden kinks in fiber coupled power

• Farfield observation– Still single ‘humped’, but shifted during kink. Still single mode? (no!)

• Standard countermeasure:– Increasing loss for higher order modes (to keep them below threshold): Does not work


Shift Kink: Lateral Mode Locking

Index moving up withtemperatureprofile (drive current)

Round

trip

conditio

n

• Waveguide– Index increases with local heating– Waveguide becomes multimode

• Dispersion characteristics of waveguide– Phase lasing condition (integer number of wavelengths in one roundtrip) can be meet for one frequency

(u0 = u1 ) for fundamental and higher order modes at the same time

Round

trip

conditio

n

For u1 = u0

Coherent coupling


Shift Kink: Coherent Coupling

1st resonantcoupling coupling

Farfield

F R F R F R F0th asymmtric

f

h

f

h

• Small asymmetry (e.g. at front mirror) couples power from fundamental tohigher order mode

• Phasematch condition given at special dispersion point (temperatureprofile,i.e. drive current):– ‘lateral mode locking’ at this current > Coherent Supermode

0th asymmtricelement

0th and 1st: Same frequency one roundtrip0th. N wavelengths1st: N-1 wavelengths


Shift Kink: Lateral Mode Locking

Coherent Supermode:

Introduction of loss for higher order modes just reduces overall efficiency

Interference within waveguide

Achtenhagen, Hardy and Harder, JQE Vol24 pp2225


Epitaxial structure

• Fast axis NA:– As long as NA<=0.5: No concern

• Of concern– High efficiency– Low loss, low series resistance– Controlled, low overlap with gain, low gamma– Controlled, low overlap with gain, low gamma


Epitaxial Structure

PVIout

VI

P

1

seshFeFhfV RRV

IEE

eVhE

eV

111

I

I

I

I leakthI 1

Resitivity:

Bandgap discontinuitiesThermal and vertical leakageInjection barriers

Material limits: Even after optimized mirror losses (Sf , Rf , Rb ) and low threshold current.– Due to limited mobility and carrier mass there are always trade-offs in

doping levels (series resistance Rs vs free carrier absorption) and Bandgap discontinuities (leakage losses vs injection barriers)

Today’s approach:– InGaAlAs material system, Electrons with low mass– Asymmetric (thin p-region), low aluminum, low confinement LOC, low doping levels

Electrons have low mass (high mobility and low density of states).

– Relatively low barriers for high mobility and good injection (some thermal and vertical leakage)

)ln(2

)ln(

)ln(1

1

ff

bf

P

R

L

R

RS

Resitivity:

Series resistanceDensity of States:

Free carrier absorption


Epitaxial Structure

Bandgap design to optimize

Doping design to optimize

Highly asymmetric physical parameters:Electron mobility: hole mobility

Resitivity:Series resistance

Density of States:Free carrier absorption

Bandgap discontinuitiesThermal and vertical leakageInjection barriers

Highly asymmetric physical parameters:Electron mobility: hole mobility

Free carrier absorption: ap = 7 - 1410-18p an = 3 - 610-18n-> Use asymmetric epitaxial structure


Epitaxial Structure

Free carrier absorption in p material is higher than in n material:- higher absorption cross section;- higher doping for comparable conductivity required;=> The design idea is to shift optical mode from p- to n-type material

Asymmetric waveguides

Mode maximum shifted from the QW position: lower FC absorption in QWValues of aFC as low as 0.4 cm-1 were reported

M. Buda et al., JSTQE, v.3, p.173 (1997) C.M. Stikley et al., SPIE Proc., v.6104, (2006)

In addition higher order modes can be suppressed


Epi structureswith low G

Asymmetric, with optical trap on nside

81

side

1.7 times decrease in G (from 1 to 2)by using the trap

G is changed by only changing thetrap width (2 & 3) – easy execution

Advantages: Lower attenuation coefficient

Lower thermal resistance

Narrow FF

Photonics 2008, Dehli

Epitaxial structures (Rsoft)

• At 5kA/cm2(calculated with Mode from Rsoft)


Epitaxial structures (Rsoft)

• Heating due to absorption


• Free carrier absorption Joule heating

vertical section

refr

acti

ve

ind

ex p-S

CH

ac

tiv

e

n-S

CH

bu

ffe

r

su

bs

tra

te

n-c

lad

din

g

p-c

lad

din

gGaN SiC Al2O3

Strain % 0.0 3.4 16

Refr. Index 2.52 2.75 1.78

GaN-Substrate, dtot = 100m

SNOM

Optical Waveguide & Substrate modes: GaN* laser diode

…

vertical section

Potential Impact ofSubstrate Modes:

- optical loss- gain oscillations

Simulation

*Source: Prof. B. Witzigmann et al., IEEE JQE 2007


Length Scaling


Length Scaling

• Increase power: Have to make laser longer to better remove the heat.• Most important laser parameters:

– Gain(G), efficincy(h), photon lifetime (tph), internal power ratio (Pr) as function of absorption(a), lenght(L), confinemnet (G), front mirror refelctivity R (for

backmirrror reflectivity=1.

• Scaling law: Keep internal power ratio constant• Scaling rule for L

• Need low loss and low confinement waveguide


980nm Single Mode Pump Diode:Length Scaling

800

1000

1200

1400

1600 G08 (2004): 3.6mm

G07 (2002)

G05 (1999)

G06 (2000)

face

tlig

ht

ou

tpu

tp

ow

er

(mW

)P-side up mountedCW-operation @ 25 °C

Improve performance by making laser chip longer

1. Low loss waveguide

2. Need facets which can sustain high powers

0 500 1000 1500 2000 2500-200

0

200

400

600

G03 (1996)

G05 (1999)

ex-f

acet

ligh

to

utp

ut

po

we

r(m

W)

injected current (mA)

G01 (1990):0.6mm

Courtesy Bookham12/11/2008 87Photonics 2008, Dehli

0.5

1

1.5

2

Lig

ht

ou

tpu

tp

ow

er

(W)

T = 5 °C

T = 25 °C

T = 50 °C

T = 75 °C

980nm single mode pump chip: 2004

T0 ~ 165 KIth ~ 45 mA @ 25°C

150MW/cm2

www.bookham.comwww.bookham.com

0

0 0.5 1 1.5 2 2.5 3

Injection current (A)

P-side up mountedCW - operation

• Reliability

– Better than 500FIT (0.5%/year) at Pop=850mW

• Wallplug Efficiency

– >60% peak, >50% up to 800mW

• Beam

– Single lateral mode beyond 1200mW, shift kink: solved

– Emission spot: 0.7um*2um

Page 88

980nm Single Mode Pump Diode:Evolution

980nm Pump Diode LasersEvolution of 980nm Single Mode Power

1000

1250

1500

1750

2000

Po

we

r[m

W] , Roll-over Power

SM FBG Fiber Power(<500FIT)

Price Reduction $/mW

Factor of 100

250

500

750

1000

1985 1990 1995 2000 2005 2010Year

Po

we

r[m

W]

(<500FIT)

980nm Pump Diode Lasers: Matured-> Power has reached plateau at 600mW .. 650mW-> Cost reduction done: Assembly in China, One platfrom for various devices-> Spectral stability and noise: Done-> High efficiency: Done (Uncooled MiniDIL)


Spectral stability


FBG stabilized

FFR, CE RG, G,CL, POL

Laser Fiber FBG

,

Wavelength stability

www.bookham.com

17nm Free Running Wavelength Shift

for 25mA - 500mA & 10°C - 40°C

=> 0.33nm/°C and 0.015nm/mA

2 nm

20 nm

Page 91

Laser Fiber FBG

,

-20

-10

0

Po

we

r(d

B)

Wavelength Stability with FBG

www.bookham.com

950 960 970 980 990 1000 1010 1020 1030-60

-50

-40

-30

25 °C550 mW

100 °C200 mW

10 °C10 mW

Po

we

r(d

B)

Wavelength (nm)

• External fiber Bragg grating to lock wavelength

Page 92

200mW G08 based un-cooled MiniDil

300

400

500

600

80oC

75oC

70oC

65oC

55oC

40oC

25oC

10oC

Po

we

r(m

W)

600 mW @ 10°C

400 mW @ 70°C

°

FBG-stabilizedCW-operation

www.bookham.com

• FBG stabilized within 1.2 nm wavelength shift from 10 °C..100 °C, 5 mW .. 200 mW• Total power dissipation @ 200 mW in fiber, 70°C: 0.52 W• Power variation is lower than 0.15db (50kHz bandwidth)

0 100 200 300 400 500 600 700 800 900 1000 11000

100

200

100oC

95oC

90oC

85oC

Po

we

r(m

W)

Current (mA)

200 mW @ 100°C

Page 93

600mW G08 based pump module

• Light output power

FBG-stabilizedCW-operation

600

800

1000

Po

we

r(m

W) 0.6

0.8

1.0

Effic

ien

cy

(W/A

)

www.bookham.com

• Light output power

– maximum module lightoutput power ~850mW

– fully FBG – stabilized,low noise (<0.1dB)

– no kink issue up to 1.5A

• Operation regime

– mainly determined by980nm pump reliability

• Module efficiency around ~0.7W/A in average

0 500 1000 15000

200

400

Po

we

r(m

W)

Current (mA)

0.0

0.2

0.4

Effic

ien

cy

(W/A

)

Page 94

JDSU 980nm Single Spatial Mode Pump

1.0

1.2

4.0

4.8

Chip LI

FBG module LI

VI

80 units

0 failures

Tj = 100C0

200

400

600

800

1000

1200

1400

Po

wer

(mW

)

© 2007 JDSU. All rights reserved.95

New FBG-stabilized pump module

– 660mW kink-free power

– 45 FIT chip reliability at 830mW

Mature package platform

– 5 billion field hours

– 5 FIT field reliability

0.0

0.2

0.4

0.6

0.8

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Drive current (A)

Ou

tpu

tp

ow

er

(W)

0.0

0.8

1.6

2.4

3.2

Vo

ltag

e(V

)

VI 0

0 500 1000 1500 2000

Time (hrs)

Passivation


980nm Single Mode Pump Diode:Time to COMD

Chemist fixed problem

Solved in 1987 (E2)


Long term reliability & COMD protection

Stimulated

EmissionAbsorption:

e-h

Non-radiative

recombination

via surface states

Free carrier absorption

Catastrophic Optical Mirror Damage (COMD)

• Facet Degradation leads to formation surface states• Surface states cause non-radiative recombination• Non-radiative recombination leads to a local increase of current injection• This leads to an increase of the local temperature• Which causes a further shrinkage of the bandgap and thus

an increase of free carriers (increased free carrier absorbtion)• Additional generation of e-h pairs leads to further absorption

of stimulated laser light causing an acceleration of the thermal run away .... COMD


FMA G08 : SEM / EBIC images

Front view

center bulk degradation front bulk degradation(without mirror damage)

front bulk degradation(with mirror damage)

Top viewUESUES


Avoid or reduce formation of non-radiative recombination states

• E2 -> Cleaving in high vacuum and in-situ passivation of the cleaved surface

• Use of InGaAsP based barrier materials -> reduced oxidation (“Al-free”) ->re-growth covering cleaved facets possible

Remove formation of non-radiative recombination states

• “Cleaving on air” -> Dry etching in vacuum -> in-situ nitridation or sulphation

Avoiding COMD

• “Cleaving on air” -> low energy hydrogen plasma or ion beam cleaning-> in situ passivation (ZnSe, Si,...)

------------------------------------------------------------------------------------------------------------------------------------

M. Gasser, E.E. Latta, "Method for mirror passivation of semiconductor laser diodes," U.S. Patent No. 5063173 M. Hu, L.D. Kinney,

M. Pessa, et al.,"Aluminium-free 980-nm laser diodes for Er-doped optical fiber amplifiers," SPIE 1995, vol. 2397, 333-341

K. Hausler, N. Kirstaedter, "Method and device for passivation of the resonator end faces of semiconductor lasers based on III-V semiconductor material,"U.S. Patent No. 7033852

L.K. Lindstrom, et al."Method to obtain contamination free laser mirrors and passivation of these," U.S. Patent No. 6812152

H. Kawanishi, et al."Semiconductor laser device with a sulfur-containing film provided between the facet and the protective film," U.S. Patent No. 5208468

E.C. Onyiriuka, M.X. Ouyang, C. E. Zah, "Passivation of semiconductor laser facets," U.S. Patent No. 6618409

P. Ressel et al. "Novel Passivation Process for the Mirror Facets of Al-Free Active-Region High-Power Semiconductor Diode Lasers," PTL 2005, vol. 17, no.5, 962-964


Reduce number of free carriers at the laser facet

• Reduce direct carrier injection without changing the bandgap(at wafer level process)

Front section isolation

• NAM (non absorbing mirrors) to reduce absorption, diffusion and thermalized carriers(at wafer level process)

Zn diffusion

Etching and subsequent re-growth of a III-V window

Avoiding COMD

Etching and subsequent re-growth of a III-V window

Si-doped and disordered windows

Vacancy induced windows (QWI)

------------------------------------------------------------------------------------------------------------------------------------

B. Schmidt et al., US Patent 6782024 - High power semiconductor laser diode

H.0. Yonezu, M. Ueno, T. Kamejima and I. Hayashi, "An AIGaAs Window Structure Laser," JQE 1979, vol. 15, no. 8, 775-781

J. Ungar, N. Bar-Chaim and I. Ury, "High-Power GaAlAs Window Lasers," EL 1986, vol. 22, no. 5, 279-280

R.L. Thornton, D.F. Welch, R.D. Burnham, T L. Paoli and P.S. Cross, "High power (2.1 W) 10-stripe AlGaAs laser arrays with Si disordered facet windows,"Appl Phys Lett 1986, vol. 49, no. 23, 1572-1574

S. Yamamura, K. Kawasaki, K. Shigihara, Y. Ota, T. Yagi and Y. Mitsui, "Highly Reliable Ridge Waveguide 980nm Pump Lasers Suitable for Submarine andMetro Application," OFC 2003, vol. 1, 398-399

J.H. Marsh, C.J. Hamilton, "Semiconductor laser," U.S. Patent No. 6760355


Effect of front section isolation (*)

Truncated Contact

Standard Contact

Reduction of current injection into front section (reduced local heating)

Reduction of free carriers (impact on the gain profile)

*Source: Prof. B. Witzigmann, ETH-Zurich


Single Mode Pump Diode:Facet passivation at 830nm and 980nm

Old (1985)Old (1985)

E1 (1986E1 (1986--7)7)E1 (1986E1 (1986--7)7)

E2 (1988E2 (1988--...)...)


290

310

330

Curr

ent(m

A)

980nm Methuselah Lasers:17 Years of Stress Test

• Conditions:– 200mW/ Ths=30°C;

150mW/ T =75°C

www.bookham.com

190

210

230

250

270

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Time (years)

Curr

ent(m

A

– 200mW/ Ths=30°C;150mW/ Ths=75°C

• Reliability at 130mW/ 25°C:– Sudden Fail: 32 FIT– No wear-out

Page 104

QWI process concept

Al

Ga

As-grown bandgap Intermixed bandgap

GaAs AlGaAsAlGaAs AlGaAs

QWI allows bandgap tuning in selected areas of the chip


160

QWI Process StepsIntense QWI technology enables high power/brightness lasers to be produced

in a manufacturing environment

• Dielectric caps are deposited on surface of wafer

• Wafer is annealed

• Quantum wells intermix with adjacent material altering the bandgap wavelength

• Wavelength change depends on properties of dielectric cap

QWI works in a variety of materials and wavelengths

• 808 nm SQW material used in this work Photoluminescence spectra

Wavelength, nm

700 720 740 760 780 800 820 840 860

PL

inte

nsi

ty,

a.u

.

0

20

40

60

80

100

120

140 SuppressedIntermixed

Intermixing cap Suppressing cap

QW

High TemperatureAnneal


150

200

250

300

350

Po

wer

(mW

)

Avoiding COMD: QWI (quantum well intermixing)

• Uncoated 830 nm lasers

• Test conditions: Initial CW measurement followed by a pulsed L-I

NAM0 nm shift

NAM45 nm shift

NAM65 nm shift

QWIregions

0

50

100

150

0 250 500 750 1000 1250 1500 1750

Current (mA)

Po

wer

(mW

)

Increase of the bandgap closeto the facet region

Reduction of free carriers

Reduction of local absorption

ConventionalLaser

Transparentoutput

waveguide


3 Years 980 nm MiniDIL Operation

• 200 mW ex-fiber at 70°C heatsink

– FBG wavelength stabilized


Assumptions

– Known failure modes

– Laser diode lifetime follows “bath tube” curve

– Infant mortality rate is vanishing or can be screened out by burn-in

– Constant failure rate (intrinsic period) is determined by sudden death(or a short wear out period followed by sudden death)

– Wear out is expected to kick in after guaranteed device life time

– Constant failure rate can be described by:

Classical life test strategy:single emitter devices

)exp( TkEPIFR bayx

www.bookham.com

tonset


Lifetest: results stress cell matrix

• All CoS post burn-in (300h, 1260mA, 85C)

Cell Power Current Junction (Case) Temperature Starts Device Hours Failures1 820 mW 1030 mA 89°C (60°C) 196 892'362 h 162 820 mW 1130 mA 116°C (80°C) 193 772'622 h 473 820 mW 1260 mA 140°C (95°C) 141 460'990 h 704 820 mW 1340 mA 151°C (100°C) 91 142'324 h 325 680 mW 1080 mA 147°C (110°C) 93 369'253 h 37

• 16 lots lots started– 2 excluded (atypical)– LV not yet applied– No selection after burn-in

• Assume functional dependence Derive• Derive parameters for which cell test results are most likely

– Maximum likelyhood analysis

5 680 mW 1080 mA 147°C (110°C) 93 369'253 h 37714 2'637'551 h 202


)(

00

0kTkT

Eyxa

ep

p

j

jFRFails

Maximum Likelyhood analysis:Ea:=0.45eV; x,y free

• X and y are anticorrelated, x+y=3.6• FR base failure rate: At 930 mA, 36°C junction temperature (25°C case)

x free, y free; Ea := 0.45 eV

x 1.5y 2.1

Ea 0.45 eV

FR 1'376 FITP 99%


)(

00

0kTkT

Eyxa

ep

p

j

jFRFails

Wavelength Range for major industrial applications /technologies requiring (red / MIR) HPL

Medical

Printing

DPSS

GaAs Capability

800nm 900nm 1000nm 1100nm700nm600nm 1400nm 1600nm

Medical Medical

InP CapabilityAlGaInP Capability

Fiber Laser Pumps FiberLaserSeeds

Direct Diode Applications

Laser TV Pumps & SHG

Nd YAGReplacement

TelcoPumps

TelcoPumps

Opticalstorage

Display,... LIDAR


Materials for Semiconductor Laser Processing


Broad Area

114Photonics 2008, Dehli12/11/2008

Broad Area

High powers are limited by power density atfacet

-> Use a wider facet, broad area laser diode:

1. higher heatload: Need to solder devicesNarrow Stripe: J-up

1. higher heatload: Need to solder devicesjunction down to heatsink

– Cooling

2. This leads to degradation of beamquality, i.e. multi lateral mode behavior

– Coupling to fiber


Broad Area: J-down

Cooling


Types of coolers for hard solder bar mounting

(*)

* Christoph Harder; “Chapter: Pump Diode Lasers”, Optical Fiber Telecommunications V A (Fifth Edition),Components and Subsystems, Editor: Ivan P. Kaminow, Tingye Li and Alan E. Willner, pp. 107-144.

- Passive Cooling (copper heat sink with heat exchanger -> Water or Air cooled)

- Active Cooling of high power bars (micro, meso or macro channel cooler)

- Active cooling of single emitter devices (TEC and heat exchanger)


9xxnm Multimode Pump DiodesHeat removal

Ball

Wedge

Golddraht

Chip

Soldered to

Submount

AuSnSoldered toexpansion matchedmaterials forheat spreading

Water

Cu

CuW

AlN CT

Em

atc

hC

TE

mis

matc

hMechanicalpressure thermalcontact to copperheatsink


Cooling: Micro Channel Coolers


Bar Blow up (Indium solder issue)

GaAs bar

Copper MCC

Coppertop contact


• Indium is used to overcome cte differencesbetween GaAs and copper

• Indium is stable under CW operation but notunder on/off operation– Increased thermal resistance leads to bar blow

up

Copper MCC

12/11/2008 120

AuSn technology on MCC


• Hard solder (AuSn) attach to expansion matched heatspreader of bar• Low smile assembly of bar on submount to MCC (this interface is still cte

mismatched)• Low stress cathode contact with wire bonds

AuSn solder unchanged after 7000 h LT(40 Mega cycles of hard on/off)

12/11/2008 121

Beamquality

2a

NA

Beam with aperture radius of “a” and divergence of “NA”The beam parameter product and the etendue is

– BPP=a*NA– Etendue=(a*NA*Pi)2, or a*b*NAx*Nay*p2 for an elliptical beam

•The minimum beam parameter product and etendue (corresponding to a single

lateral mode) is given by– BPP=a*NA=Lambda/ p =0.32um*rad for lambda=1um– Etendue=(a*NA* p)2=Lambda2=1*10-8 cm2 ster for lambda =1um


9xxnm Multimode Pump Diodes:Thermal Blooming at high PowerTop view of BA laser

NAdn

n

dT

Issues of Low NA lasers

0.003

0.004

0.005

0.006

dn

Low NA laser Achieved by low dn waveguide

dn Ridge

Lateral temperature profile

dT=5K -> NA=0.09

Keep dT<5K

0

0.001

0.002

0.003

0 0.05 0.1 0.15 0.2

NA

dn

dT=5K


0 2 4 6 8 10 120

2

4

6

8

10

12

CW m easurem entp-side down m ounted on C-m ount

lig

ht

ou

tpu

tp

ow

er

(W)

15°C25°C55°C75°C

SES8-9xx-01 performance

CW= 960 nm

www.bookham.com

0 2 4 6 8 10 12

injection current (A)

• Electro-Optical

– Power: 8 W @ 8 A

– Reliability: <5% fail in 10‘000h

30

25

20

15

10

5

0

po

wer

(W)

3020100

current (A)

Q-CW(0.3ms)

Page 124

Number of Lateral Modes in BA chip

100um BA, #of modes

15

20

25

30

35

40

Nu

mb

er

of

mo

des

,

• Low NA broad area laser radiance:– Closing in on single mode lasers– 8W from NA=0.15NA: 400mW per lateral mode

• Reduce NA of broad area laser to increase radiance– NA dominated by thermal blooming– ->Need chip with very high power conversion

0

5

10

0 0.1 0.2

NA

Nu

mb

er

of

mo

des

,


High Power Laser Diodes: 20 years ago

• Narrow stripe laser:– COMD: Mirror blows up at high powers

-> Spread beam to decrease powerdensity at facet:

Coherent arraysSurface grating lasers

In the 80‘

Never achieved reliablebeamstability for highvolume applications

Surface grating lasersMOPATaper LaserAlpha DFBVCSEL


1-D Active Photonic Crystal ROW Array

Index

Gain

3.427

3.403

Resonant Mode at S = 1.0 mm

S 4 mm

I = 9 x Ith

1.6 W CW ( l= 0.98 mm)

Resonant (lateral) leaky-wave coupling

Bragg condition exactly satisfied

(20 - 40)-element phase-locked arrays

15.010.05.0-15.0 -10.0 -5.0 0.0

Angle (Degrees)

q1/2= 0.67° = 1.8 x D.L.hp= 23%

1.0 W power in main lobe40-element 200 mm aperture *

* H, Yang et al., Appl. Phys. Lett., 76, 1219 (2000)

9xxnm MM Pump Diode: CW on C-mount

20

15

10

5

ou

tpu

tp

ow

er(W

)

15ºC25ºC35ºC

www.bookham.com

• ~90 um emission width

• 19 W CW roll over power at 15 C

• Temperature insensitive: To ~ 200K

• At 35 C

– 9 W at 9 A

– >65% conversion efficiency at9W

current (A)

0

ou

tpu

tp

ow

er(W

)

242220181614121086420

35ºC45ºC

Page 128

Etendue Matching

Theoretical limits:• 4800 single mode lasers fit in a 200um/0.22NA fiber• 350 Standard BA lasers fit in a 200um/0.22NA fiberWith polarization multiplexing and wavelength division multiplexing even mor

diodes can fir in the fiber


MM Uncooled Module with >14W

6

8

10

12

14

16

Ex

-Fib

reP

ow

er

(W)

10°C

25°C

45°C

www.bookham.com

• Record Performance:

– >14W @ 18A and 10 C Ths

• Module fully qualified for industrial and telecom standards

– 8W Industrial Product

0

2

4

6

0 2 4 6 8 10 12 14 16 18 20

injection current (A)

Ex

-Fib

reP

ow

er

(W)

Page 130

• Module

– 3 single emitters inside

– 2-pin package

– 0.15NA or 0.22NA in 105um fiber

– Floating anode/cathode

– 1060nm blocking filter included

Example II: 20W Multi-Emitter Module

P-I -V Curves of 0.15NA 20W Modules at 25C:30 6


• Electro-Optical

– Power: 20+W

– Current: <<10A

– Wavelengths: 915, 940, 960, 975nm

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12

Diode Current (A)

Lig

htP

ow

er

(W)

0

1

2

3

4

5

Dio

de

Vo

lta

ge

(V)


New generation 9xx broad area chip

T=15C

10

15

20

25

30

Po

wer,

W

pulsed

CW

2

4

6

8

10

12

14

16

Po

we

r,W

25C

35C

45C

55C

70C

90C


19.0W maximum CW power from ~ 100um aperture

0

5

0 5 10 15 20 25 30

Current, A

0

2

0 5 10 15

Current, A

T=15C0

5

10

15

20

25

30

0 5 10 15 20 25 30

Ou

tpu

tp

ow

er

(W)

pulsed

CW

JDSU 9XXnm Multi Mode Pump

Cell 4, 11.1W average power, 14A, 113C

0

2

4

6

8

10

12

14

0 1000 2000 3000 4000

Po

we

r,W


Drive current (A)

100mm wide aperture chip– 20W CW rollover power

105mm diameter, 0.2NA fiber– 8W rated power at 10A

Commercial 6397-L3 Design CW Operation

0

2

4

6

8

10

0 2 4 6 8 10 12

Current (A)

xF

ibe

rP

ow

er

(W)

20C

30C

40C

0 1000 2000 3000 4000

Time. hrs

6396 Chip Reliability Improvement

MLE Results:

hrs

n

eVE

op

A

6101.5

7.2

61.0

54.0

50%

90%

99%

Unre

liabili

ty

6396 c

6390

6390

6396


Revised reliability:– P=8.0W

– Th=35C

– Median time to failure=1,500,000 hrs (60% C.L.)

– 6% F at 20khr (60% C.L.) 1%

5%

10%

1000.00 1.00E+610000.00 1.00E+5Time, hrs

Unre

liabili

ty

Example: JDSU L4 module performance & testing

Laser chip– InAlGaAs

– 880-1000nm

– 100mm aperture

– 4.1mm cavity

– AuSn solder 15

20

25

Po

we

r(W

) 45%

60%

75%

Pow

er

co

nve

rsio

nE

ffic

ien

cy

.

ex-facet

ex-fiber

© 2008 JDSU. All rights reserved. SSDLTR June 2008135

Fiber-coupled package– 105mm diameter

– 0.15 or 0.22NA

– Rth = 2.2oC/W

– 10W rated power

– 50% wall plug 0

5

10

0 5 10 15 20 25

Current (A)

Po

we

r(W

)0%

15%

30%

Pow

er

co

nve

rsio

nE

ffic

ien

cy

.

15C


Accelerated life test examples

Chip Life Test– 9.3W, 13A

– Tcase = 70oC

– Tj = 117oC

– 28 lasers

– 0 failures


-10%

-5%

0%

5%

10%

0 1,000 2,000 3,000 4,000

Time (hours)

Po

we

rC

ha

ng

e

Package Test– 10W, 12A

– Tcase = 35oC

– 14 lasers

– 0 failures


L4 Package qualification and robustness tests

-10%

-5%

0%

5%

10%

Time

Zero

Mech

Shock

Vibration

De

lta

Po

we

r

500G Mechanical Shock+ 20G Vibration Reference Telcordia GR-468

– Zero package failures in full suite

– Proves robustness of design

12 units

10%85C / 85% RH Damp Heat


-10%

-5%

0%

5%

10%

0 100 200 300 400 500

No of CyclesD

elta

Po

we

r

-40C to +85CTemperature Cycling

27 units

-10%

-5%

0%

5%

10%

0 1000 2000 3000 4000 5000

Time (hours)

De

lta

Po

we

r

18 units


Pump power trends – commercially available

15% annualincrease in reliablepower

Similar trend for

10

Fib

er-

co

up

led

CW

Po

we

r(W

)

L3-6397

L3-6390

L4-6398

L3-6396

L2-6380


Similar trend for– 8XXnm

– Single mode lasers

– Multi mode lasers

– Bars1

1992 1994 1996 1998 2000 2002 2004 2006 2008

Year

Fib

er-

co

up

led

CW

Po

we

r(W

)

9XXnm 105mm diameter fiber “Reliable” rated power


Example III: FiberExample III: Fiber Coupled Devices of 2006 designCoupled Devices of 2006 design::PLDPLD--2020--9xx9xx series based on L=3.0mm COS: Ø=100 mm fiber, NA < 0.12

139 12/11/2008 AHPSL 2008 Seminar #1 Photonics 2008, Dehli

Example IV: FiberExample IV: Fiber Coupled Devices of 2008 design:Coupled Devices of 2008 design:PLDPLD--3030--9xx9xx series (based on L=4.5mm COS): Ø=100 mm fiber , NA < 0.12

140 12/11/2008 AHPSL 2008 Seminar #1 Photonics 2008, Dehli



Example I: Second-Generation Fiber Pump Modules

• Characteristics

– Multiple emitters (e.g., a single mini-bar)

– Micro-optics for beam conditioning

– More power in (e.g., higher current at std voltage)

• Features

143

H2 short presentation

• Features

– Enhanced brightness per fiber channel

– Reduced thermal and electrical resistance (higher power at rollover)

– CoS with single-emitter economies, no smile

– Independent dropouts, reduced facet loading, enhance reliability

– Highly scalable at module level


• Brightness of industrial modules now exceeds 1 MW/cm2-sr

e.g.,

- 20W, 105um core, 0.20NA

- 915nm, 940nm, 976nm

Mini-Bar Fiber Pump Module

Orion™ series

3.8cm

30 0.6

144


- mini-bar architecture

- very high reliability

0

5

10

15

20

25

0 5 10 15 20 25 30 35

Current (A)

Po

wer

(W)

0

0.1

0.2

0.3

0.4

0.5

PC

E

Power

PCE

Specified Operating Pt


Mini-Bar Reliability: verification of emitter independence

CoS: 5-element mini-bar on CT

(AuSn solder on CuW heatsink)

single-emitter failures

145


Multi-Stripe Modules as Ensembles of Semi-Independent Emitters:

• failures are dominated by random, sudden failures of individual emitters

• the failure of an individual emitter only impacts other emitters by an increase in ensemble drivecurrent (for constant power) and warming of the other stripes on the same mini-bar

• all assumptions are consistent with test data giving over 300,000 hrs MTBEF (mean timebetween emitter failure) at the specified operating point

single-emitter failures


Fiber combinerFused and Proximity

Fused: (6+1)*1 Proximity: (2+1)*1

Fused can be extended to beyond 20 inputsProximity needs high brightness pumps

Fiber NA

Signal input HI 1060

Pump Ports 6*105um 0.22

Output 20um/400um 0.06/0.46


Pump power injectionCoaxial dual claddingCoaxial cladding400um, NA=0.46: 150’000 modes


Fiber Laser: MOPA

Seed laser

Pump Diode

Dual Clad Yb

MMPMFPMF

• Seed laser– Fiber laser: Good spectral control

Need external modulators (Pockels Cell)– Diode laser: Excellent dynamic control

FP laser have poor spectral control, of no concern DFB have excellent spectral and dynamic control

• Pumplaser– High Brightness: Single emitter broad area 9xxnm MM diode

Seed laserPump Diode


Scalability of Fiber Laser

• Serial

• Parallel– Coherent Incoherent

~

~ ~

~

~


Power Photonics: Fiber LaserFiber Delivered Beam Machining Tool

• Solid State– Hermetically sealed Diodes coupled to Fibers– Fiber delivery

• Technology– Apply telecom technology to power photonics

Page 150

‘SM’ fiber Fiber laser


9xxnm 120W Bar Performance

P-I curve at 25Cup to 200W:

• Electro-Optical

– Power: 120W @ 140A

– Threshold: 14A

– Slope Eff.: 1W/A

• Reliability0

25

50

75

100

125

150

175

200

Po

wer

(W)

www.bookham.com

Condition 120W pulsed (1.33Hz, 0<->140A)

• Reliability

– 5’200h at 120W lifetest dataat 1.33Hz full on/off pulsedconditions available

– The extrapolated medianlifetime is above 80’000hrs or350 MShots, less than 1%fails after 120 MShots.

– No open fails

0

0 100 200

Current (A)

0.5

0.6

0.7

0.8

0.9

1

1.1

0 1000 2000 3000 4000 5000 6000

Time (h)

Rel.

po

wer

(a.u

.)

Page 151

Bar with 425W CW at 980nm

400

300

200

CW

pow

er(W

)

www.bookham.com

– 425W at 980nm, 1cm, 50% FF

– On standard MCC

– 3.6mm long laser cavity

200

100

0

CW

pow

er(W

)

6005004003002001000

current (A)

Page 152

High-efficiency bars

Performance of JDSU/SHEDS 100W Bars

50

75

100

125

150

Ou

tpu

tP

ow

er

(W)

60%

65%

70%

75%

80%

Po

we

rC

on

ve

rsio

nE

fficie

nc

y


>75% wall plug efficiency from 120W 940nm bar(SHEDS design)

0

25

50

0 20 40 60 80 100 120

Drive Current (A)

Ou

tpu

tP

ow

er

(W)

50%

55%

60%

Po

we

rC

on

ve

rsio

nE

fficie

nc

y

Results – Compare FF = 50% to FF = 33% Mesochannel Compact Heat Exchanger (MesCHE)

Rth = 0.38 C/W

L = 3.5 mm160

180

200

220

240

Po

we

r(W

)40

50

60

EO

Eff

icie

nc

y(%

)

Tj = 60 C

MesCHE

12/11/2008Photonics 2008, Dehli 154

L = 3.5 mm

P = 127 W (FF=50%)

P = 151 W (FF=33%)

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140 160 180 200 220

Po

we

r(W

)

0

10

20

30

Current (A)

EO

Eff

icie

nc

y(%

)

FF=50% ModelFF=50% DataFF=33% ModelFF=33% DataFF=50% Model


Results – Compare FF = 50% to FF = 33%Microchannel Cooler (MCC)

210

240

270

300

50

60

70

EO

Eff

icie

nc

y(%

)

MCC

Tj = 60 C

Rth = 0.23 C/W

L = 3.5 mm

12/11/2008Photonics 2008, Dehli 155

0

30

60

90

120

150

180

0 50 100 150 200 250

Current (A)

Po

wer

(W)

0

10

20

30

40

EO

Eff

icie

nc

y(%

)

FF=50% ModelFF=50% DataFF=33% ModelFF=33% DataFF=50% Model

L = 3.5 mm

P = 200 W (FF=50%)

P = 207 W (FF=33%)


Reducing Complexity: 9xx 1/3 size VHB Bar

0.6

0.7

0.8

0.9

1

1.1

no

rma

lize

do

utp

ut

po

we

r(a

.u.)

90W / 100A40

60

80

100

120

140

160

Vo

ltag

e(V

)

CW Room Temperature

Lig

ht

Ou

tpu

tP

ow

er

(W)

Wallp

lug

Eff

icie

ncy

(%)

0.5

1.0

1.5

2.0

10

20

30

40

50

60

Power 80 W Theatsink

25°C

Inte

nsi

ty(a

.u.)

40

60

80

100

120

140

160

Vo

ltag

e(V

)

CW Room Temperature

Lig

ht

Ou

tpu

tP

ow

er

(W)

Wallp

lug

Eff

icie

ncy

(%)

0.5

1.0

1.5

2.0

10

20

30

40

50

60

Power 80 W Theatsink

25°C

Inte

nsi

ty(a

.u.)


• Reduced 1/3 size BAR on MCC

– Significant reduction on complexity of high power systems due to high totalpower from actively cooled MCC

– Maintain drive currents below 100A at increased brightness (bar size)

• Efficiency >55%, smile 1um, lat. farfield 8° (90% power)

– Highly reliable operation (hard pulse 1.3 Hz, 50% duty cycle, full ON-OFF)

• Power wear-out <1% / 1000h

0.5

0.6

0 1000 2000 3000 4000 5000

time (h)

no

rma

lize

do

utp

ut

po

we

r(a

.u.)

90W / 100A

0 50 100 150 2000

20

Injection Current (A)

0.0 0

10

970 980 990Wavelength (nm)

0 50 100 150 2000

20

Injection Current (A)

0.0 0

10

970 980 990Wavelength (nm)


Challenges for the design of HPL:Bar Bonding – Low Smile and High Current Capability

Subsystem design

• Submount material (expansion matched)• Robust cooler design (avoid corrosion)• Strain – Stress (reduced at all interfaces)• low Smile (hard solder, low smile)

Picture with courtesy of

• low Smile (hard solder, low smile)• Passive optics design (efficient)• Fiber diameter (low core, low NA)


Bar multiplexing to achieve highest opticalpower densities for direct application

Picture with courtesy of

158

Wavelength division multiplexing

High Power Single Mode Laser Diode

EDFA: Killer application: Done and dusted

used now for printing


Direct Coupled Diodes:

• Practical limits to radiance?


9xxnm Multimode Pump Diodes:Machining directly with Pump Diodes

200um,0.22

600um,0.22

1500um,0.22

Direct Diode

• Single Mode Pump Diode: 1W• Multimode Pump Diode: 0.5W/mode

– Low cost packaging needed

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

0 200 400 600 800 1000 1200 1400 1600

Diameter (um)N

um

ber

of

Mo

des

,

(bo

thP

ol)

,

Number of Modes in Fiber

50um.0.22


About the author

• Professional Summary

Dr. Christoph Harder has received the Electrical Engineering Diplomafrom the ETH in 1979, Zurich, Switzerland and the Master and PhD inElectrical Engineering in 1980 and 1983 from Caltech, Pasadena, USA.Christoph is co-founder of the IBM Zurich Laser Diode Enterprise whichpioneered, among other laser diodes, the first 980nm high powerpump laser for telecom optical amplifiers. It is estimated that todaymore than 50% of the internet links (including intercontinentalcommunication) are powered up by such laser diodes, eithermanufactured in Zurich (majority) or by licensed partners.


manufactured in Zurich (majority) or by licensed partners.

Christoph has been managing during the last few years the high powerlaser diode R&D effort in Zurich expanding, working closely with amultitude of customers, the product range into 14xx pumps as well as808 and 9xx multimode pumps for industrial applications. Dr. Harderhas published more than 100 papers and 20 patents and has held avariety of staff and management positions at ETH, Caltech, IBM,Uniphase, JDS Uniphase, Nortel and Bookham.

Dr. Harder was General Chair of the International Semiconductor LaserConference and the LEOS Annual Meeting, was on the board ofIEEE/LEOS and has served on numerous technical program and steeringcommittees. Today he is active on the board of OSA, BHL, President ofSwisslaser.net and on the direction committee of NCCR QP.

Dr. Christoph HarderHarder&Partner

Email:[email protected]:www.charder.ch

Documents

Pump Diode Lasers: Applications and Technology