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Infrared sources: a comparative study

Antoine GODARD

DPMH ­ Physics, Instrumentation and Sensing Department Journées Scientifiques de l'Onera, 5-6 février 2007 Sources paramétriques pour l'infrarouge

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

3

Context

·

Civilian applications

·

Atmospheric pollution monitoring (CO, NOx,HF, CH4...) Industrial process control Combustion or hypersonic flows monitoring Medical diagnosis of disease Free-space communications Detection of neurotoxics (Hyperite, Sarin...) Infrared imaging and tracking Countermeasures

· · · ·

·

Defense and security

· · ·

·

In this presentation:

· ·

Spectral range is restricted to 2 ­12 µm Only CW and nanosecond pulsed operation are considered

4

How to make the good choice ?

·

Technologies

·

Rare-earth crystalline and fiber lasers

· Er · Tm · Ho

·

Requirements

· · · · · · · ·

High power (or not) Pulsed / CW Narrow linewidth (or not) Tunability Central wavelength Beam quality Beam polarization ...

·

?

· ·

Transition metal vibronic lasers

· Cr · (Fe)

Semiconductor lasers

· GaInAsSb heterojunction · Quantum cascade lasers

Parametric sources

· OPO · DFG

5

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

6

Selected technologies

Technology Tm laser Ho laser Er laser Cr:laser Parametric sources Antimonide DH lasers QCL Points detailed in this presentation 2 µm Tm:crystal ­ tunability and power 2 µm Tm:fiber ­ CW 2.1 µm Ho:crystal ­ energy and power 2.1 µm Ho:fiber ­ CW 3 µm Er:crystal ­ diode pumped 3 µm Er:fiber ­ CW Cr:ZnSe ­ pulsed Miniature high rep. rate OPOs Single frequency tunable OPOs OPOs above 5 µm High power structures Tunable lasers High power structures Tunable lasers Application : trace gas sensing Points skipped in this presentation 2.3 µm Tm:crystal ­ tunability and power 2 µm Tm:fiber ­ pulsed 3 µm Ho:fiber ­ CW 3 µm Er:crystal ­ high energy 3 µm Er:crystal ­ CW tunability Cr:ZnSe ­ CW Hot topics ­ electrical pumping, Fe:ZnSe 2-µm power and energy OPOs Example : CdSe OPO for mid-IR DFG in OP-GaAs for CRDS

7

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

8

Tm3+-based lasers

~2.3 µm

Summary · Two laser transitions

· ·

1.9­2 µm ( 3H4? 3H6) 2.2­2.4 µm ( 3F4? 3H5)

El-Sherif et al, JQE 39 (2003) 759

·

Host :

· ·

Crystals : YLF, YAG, YSGG, YAlO3, GdVO4 ,... Fiber : silica, ZBLAN,...

· · · ·

Tunable Diode pumping

·

780­795 nm or 805­810 nm (GdVO 4 and YVO4 host matrices)

CW as well as pulsed operation is possible Attractive pump laser for Cr:ZnSe and Ho:crystal

9

Tm3+-based crystalline lasers @ 2 µm

·

Wide tunability (~300 nm)

·

Multi-watt output power

· ·

120 W at 2.01 µm (M2 ~ 20) CW 30 W at 2 µm (nearly diffraction limited) CW and pulsed (several kHz)

Coluccelli et al, APB 85 (2006) 553

Budni et al, JOSAB 17 (2000) 723

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Ho3+-based lasers

Summary · Two laser transitions

· ·

1.95­2.15 µm ( 5I7? 5I8) 2.85­3.05 µm ( 5I6? 5I7) self-terminated transition Crystals: YAG, YLF, YSGG,... Fibers: silica, ZBLAN

·

Host

· ·

Jackson, JQE 42 (2006) 187

· ·

Discrete tunability (several individual spectral lines) Diode pumping

·

·

780 nm with Tm co-doping (upconversion problem for high average power) 1.9 µm direct pumping (0.7 W output)

· ·

11

CW as well as pulsed operation is possible Common pump for ZGP OPOs

Ho3+-based crystalline lasers at 2.1 µm

·

(Very) high pulse energy

· ·

1 J (190 ns, 2 Hz rep. rate) M2 < 1.5

Yu et al, OL 31 (2006) 462

12

Ho3+-based crystalline lasers at 2.1 µm

·

Multi-watt average power

·

Diffraction limited (TEM00)

Dergachevet al, ASSP 2003

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Tm3+ ­Ho3+-based fiber lasers

·

·

150 W CW nearly diffraction limited in Tm doped silica fiber (commercial products) Tunable emission can be achieved

· · ·

1.75­2.1 µm with Tm doping, up to 2.2 µm with Ho co-doping (limited by silica multi- phonon absorption) Longer wavelength with doped IR fibers (ZBLAN)

Lancaster et al, ASSP 2007

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3-µm Er 3+-based lasers

Summary · Laser operation in the 2.58­2.94 µm range (4I11/2? 4 I13/2) · Discrete tuning (several individual spectral lines) · Host

· ·

Crystals: YAG, YLF, YSGG,... Fibers: ZBLAN

Stoneman et al, JQE 28 (1992) 1041

· ·

·

Diode pumping possible at 970 nm CW as well as pulsed operation was demonstrated despite the self-terminated 3 µm transition Coincide with O-H vibration in water

· · ·

Attractive for laser surgery and ophtalmology Can be used as an OPO pump Unsuited for free-space propagation

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Er 3+-based crystalline lasers

·

Pulsed operation

· · ·

Diode pumped High rep rate (up to 600 Hz) 3 W average power (30 mJ, 100 Hz)

Ziolek et al, OL 26 (2001) 599

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3-µm Er 3+-based fiber lasers

·

Population bottleneck problem

· ·

Pr co-doping High Er doping concentration

· ·

Up to 10 W CW (single mode beam) Medical applications

Zhu et al, OL 32 (2007) 26

17

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

18

Cr 2+-based lasers

Summary · Laser operation demonstrated in the 1.9­3.1 µm range (5E? 5T 2) · Wide continuous tuning (vibronic laser) · Host: semiconductors (ZnSe, ZnS, CdSe,...) · Short excited state lifetime (6­8 µs at 300 K)

·

gain-switching in pulsed regime

Fedorov et al, JQE 42 (2006) 907

·

Applications

· · Tm:YLF Tm:CaF 2

Direct emission in the whole 2­2.4 µm band Mid- IR OPO pumping

pulsed operation Cr:ZnSe

Sorokin et al., IEEE JSTQE 11 (2005) 690

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Tm:fiber

Cr 2+:ZnSe laser ­ pulsed regime

·

Pulsed pump required

· ·

·

Fast tunability

· · ·

t ~ 6 ­8 µs Q-switched Tm pump lasers Gain-switched Pump : Tm:YALO 30 W at 7 kHz Laser : 18,5 W

Gain-switched and Q-switched (EO) Pump : Tm:YALO 20 W at 5 kHz Intra-cavity acousto-optical filter

·

Maximal output power

· ·

Zakel et al., TOPS ASSP 2005, 98 (2005) 723

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Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

21

Antimonide-based semiconductor lasers

Summary · MQW GaIn(As)Sb/AlGaAsSb system can cover efficiently the 2­3 µm range · Emitted wavelength depends on the alloy composition · CW room temperature operation demonstrated in the 1.9­2.8 µm range · Various choice of structures

· · ·

Joullié et al, IEEE JSTQE 5 (1999) 711

Fabry-Perot heterojunction laser Tunable and single frequency laser (DFB, ECL,...) High power laser (broad stripe, tapered, bars,...)

· ·

Short carrier lifetime (~1 ns) no energy storage (CW or quasi-CW) Applications

· ·

Gas sensing IR laser pumping

Band gap Eg

?1

changed alloy composition Eg1 Eg2

?2 < ?1

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Antimonide-based semiconductor lasers

·

High power structures

· · ·

> 2 W single emitter > 15 W bar > 1.5 W nearly diffraction limited

10

Pfahler et al, PTL 18 (2006) 758

CW Power (W)

Broad stripe Bar Tapered structure

1

0.1 1.8 2.0 2.2 2.4 2.6

Walpole et al, PTL 11 (1999) 1223

Wavelength (µm)

23

Antimonide-based semiconductor lasers

·

Tunable and narrow linewidth lasers

· ·

DFB ECL

Geerlings et al, PTL 18 (2006) 1913

Hümmer et al, PTL 16 (2004) 380

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Quantum Cascade Lasers

Summary · InP based ? > 3 µm, GaAs based ? > 8 µm · Emitted wavelength engineered (fixed by QW thickness) · CW room temperature operation demonstrated in the 4.3­9.5 µm range · Short carrier lifetime (~1 ps) no energy storage (CW or quasi-CW) · Delicate thermal heating management · Useful for in situ trace gas sensing

Same alloy ?1 changed QW thickness ?2 > ?1 Conduction band discontinuity

Sirtori et al, C. R. Physique 4 (2003) 639

Capasso et al, IEEE JSTQE 6 (2000) 931

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Quantum Cascade Lasers

·

Output power

· · ·

~ 800 mW room temperature quasi- CW ~ 600 mW room temperature CW Slivken et al, APL 80 (2002) 4091 Limitation due to the large amount of heat that must be dissipat ed from a small volume (~ 10 W in a 5 µm × 20 µm × 2 mm volume)

800 Power (mW) 600 400 200 0 2003 2004 Time (year) 2005

800

= 6 µm

? = 8.9 µm

CW - T = 300 K

Average power (mW)

600

400

200

CW - T = 300 K CW - T > 250 K quasi-CW - T = 300 K

0 4

26

Forget et al, EL 41 (2005) 418

5

6

7

8

9

10

Wavelength (µm)

Quantum Cascade Lasers

·

Tunable and narrow linewidth lasers

Kennedy et al, APL 89 (2006) 201117 Maulini et al, APL 84 (2004) 1659

Maulini et al, OL 30 (2005) 2584

Wittmann et al, APL 89 (2006) 141116

27

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

28

Parametric sources

Summary · Extend lasers to the whole 2­12 µm range by nonlinear conversion · (Very) broad continuous tuning range

·

3.9­11.3 µm (AGS OPO 1), 3.8­12.4 µm (ZGP OPO2), 3.3­19 µm (GaSe OPG 3)

· · ·

CW as well as pulsed operation PP-materials for ? < 4.5 µm (?pump ~ 1 µm) otherwise ?pump > 2 µm Nonlinear interactions can be engineered in PP-materials

ZGP OPO

PPLN/PPKTP/PPLT ZGP CdSe AGSe

1 Vodopyanov et al, APL 75 (1999) 1204 2 Vodopyanov et al, OL 25 (2000) 841 3 Vodopyanov JOSA B 16 (1999) 1579 ,

AGS OP-GaAs 2 4 6 8 1012

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Wavelength (µm)

Miniature high rep. rate PPLN OPO

·

Quantum conversion eff. (%)

Typical lab results

· · ·

High conversion efficiency Good beam quality Compact design

0,12

40

20

0,10

Y (mm)

0,08

PPLN OPO

0 0 2 4 6 8 10 12 14

0,06

Average power Nd:YAG (W)

0,04 0,04 0,06 0,08 0,10

1000

X (mm)

Waist (µm)

800 600 400 200 0 0

Normalized Intensity

Waist (µm) 2 M = 1,58

1.0 0.8 0.6 0.4 0.2 0.0 0 200

Depleted pump Input pump OPO

10

20

30

400

600

800

Distance (mm)

30

Time (ns)

Single frequency tunable ECOPO

·

Versatile device

· · ·

Automated tuning

Optical transmission

N2 O (~3.9 µm) as well as CO 2 (~4.2 µm) with the same device Low threshold (microchip laser pump source) 1.0

0.5 0.0 1.0 0.5 0.0 2560 2565 -1 Idler frequency [cm ]

N2O

?/2 µ laser I 3920 nm M5 PZT M1 PZT M4 PPLN PZT M3 1460 nm Fibre 1064 nm

Optical transmission

1.0 0.5 0.0 1.0 0.5 0.0 Hitran

M2

Idler Freq. [cm-1]

2488.0 2487.5 2487.0 0 1 2 3 4 5 6 7 Time [min]

PC Labview

CO2

µ FP

Scherrer et al, JOSAB 17 (2000) 1716 Desormeaux et al, OL 29 (2004) 2887 Berrou et al, Europhoton 2006

Experiment 2385 2390 Idler frequency [cm -1 ]

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OPOs with materials suitable for ? > 5 µm

·

Comparison of materials

· · ·

ZGP suitable for high power/energy applications CdSe interesting for ? > 8 µm but needs tunable pump OP- GaAs : emerging nonlinear optical materials (PPLN of the mid- IR ?)

Pulse energy

10

Average power

10

1

Average power (W)

Pulse energy (mJ)

0.1

CdSe AGS AGSe ZGP OP-GaAs

3 4 5 6 7 8 9 10 11 12

1

CdSe AGSe ZGP OP-GaAs

3 4 5 6 7 8 9 10 11 12

0.1

Wavelength (µm)

32

Wavelength (µm)

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

33

Spectral coverage

· · ·

Strongly depends on the technology Limited choice above 3 µm The efficient actual spectral coverage of a single emitter is (usually) much smaller !

Parametric sources QCL InGaASb diodes Er:crystal Cr:ZnSe Tm,Ho:silica fibre Ho:crystal Tm:crystal 2 4 6 8 10 12

Wavelength (µm)

34

2­3 µm range

Parametric sources QCL InGaASb diodes Er:crystal

·

Summary of main features

Cr:ZnSe Tm,Ho:silica fibre Ho:crystal

Technology Laser diodes CW or quasi CW > 2 W / emitter ­ 200 nm with low power Electrical (or optical)

Rare-earth lasers CW as well as pulsed > 100 W > 1 J (Ho) 300 nm (Tm)

Cr:ZnSe lasers CW or pulsed (with pulsed pump) ~ 2 W (CW) ~ 20 W (pulsed) ~ 3 mJ 1 200 nm Diode or laser (maybe electrical)

Parametric sources Pulsed (with pulsed pump) or CW ~ 50 W ~ 300 mJ Full range

Tm:crystal 2

3

Regime Average power Energy Tunability

Pumping

Diode or laser

Laser

35

2­3 µm range selected applications

·

Parametric sources QCL InGaASb diodes Er:crystal

In situ chemical sensing (abs. spectroscopy, CRDS)

· ·

Cr:ZnSe Tm,Ho:silica fibre Ho:crystal Tm:crystal 2

3

Limited tunability ? laser diodes (DFB, ECL) Broad tunability ? parametric sources, Cr:ZnSe lasers

·

Lidar and nonlinear spectroscopy (CARS, FWM)

· ·

Limited tunability ? Tm­Ho lasers, OPOs, Cr:ZnSe lasers Broad tunability ? OPOs, Cr:ZnSe lasers

·

Laser and OPO pumping

· · ·

Cr:ZnSe laser pumping ? high power laser diodes, Tm lasers (, OPO) Ho laser pumping ? Tm lasers, (laser diodes with Tm co-doping) OPO pumping ? all (except laser diodes), depends on the OPO crystals (absorption, phase matching conditions, ...)

·

Surgery

·

Er and Ho laser at 3 µm

36

3­12 µm range

·

2 options (actually 3 with CO2 laser...)

CO2 lasers Quantum cascade lasers Parametric sources Pulsed (with pulsed pump) or CW > 10 W ~ 1 W (? > 8 µm, pump limited) ~ 30 mJ ~ 10 mJ (? > 8 µm) ~ 8 600 nm (OPO) ~15 700 nm (OPG) Laser

Technology

Regime Average power Energy

CW or quasi -CW ~ 400 W (compact systems) ­ Discrete 9.15­9.83 µm + 10.09­10.93 µm Electrical

CW or quasi -CW ~ 1 W (? > 4.5 µm) ­ ~ 400 nm low power ~ 2 000 nm very low power Electrical

Tunability Pumping

37

3­12 µm range selected applications

·

In situ chemical sensing (abs. spectroscopy, CRDS)

· ·

Limited tunability ? QCL Broad tunability ? parametric sources

·

Lidar and nonlinear spectroscopy (CARS, FWM)

· ·

Limited tunability ? OPOs Broad tunability ? OPOs

·

Military applications

· ·

CW with moderate average power and tunability ? QCL High peak and/or average power with broad tunability ? OPOs

·

Cutting and welding

·

Very high average power with limited tunability ? CO2 laser

38

Outline Introduction / context Review of selected technologies

· · · ·

· ·

Rare earth doped lasers (Er, Tm, Ho) Transition metal doped lasers (Cr) Semiconductor lasers (Antimonide-based DH, QCL) Parametric sources (OPO, DFG) 2­3 µm spectral range 3­12 µm spectral range

·

Discussion

· ·

·

Conclusion

39

Conclusion

Short review of the main coherent sources technologies in the 2­12 µm range The reported technologies are complementary and relevant depending on the considered application

·

·

·

similar to the visible/near- IR range where several technologies coexist

·

Above 3 µm the choice is limited to two solid-state technologies

· ·

Parametric sources Quantum cascade lasers

·

Suggested reference

·

I. T. Sorokina and K. L. Vodopyanov, Solid-State Mid-Infrared Laser Sources, Springer (2003)

40

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