DILAS Diode Lasers used in Defense Applications March … · Alkali vapormedium: ... DPAL Summary...

New Diode Lasers used in

Defense Applications

March 2012

Dr. Joerg Neukum

Solutions for Defense Laser Applications

All Colors – All Packages

HPDL in Defense Applications

Abstract

• Diode Lasers have a broad wavelength range, ranging from the visible to beyond 2.2µm. This allows a whole lot of applications in the defense sector, ranging from classic pumping of DPSSL in range finders or target designators, up to pumping directed energy weapons in the 50+kW range. Also direct diode applications for illumination above 1.55µm, or direct IR countermeasures are of interest. Latest developments of light-weight 976nm fiber-coupled pump modules (300W out of 300gramm) will also be described, as well as new wavelengths for applications of diode-pumped alkaline lasers (DPAL).

2Proprietary Information


Outline

• High Power CW 808 / 880 / 940nm

• DPAL – Diode Pumped Alkaline Lasers

• > 1.0 µm HPDL

• Scalable Fiber Coupled Mini-Bar Concept

• Light Weight Fiber Coupled Mini-Bar-Concept


HPDL in Defense Applications 4Proprietary Information

High-Power 8xx & 9xx nmCW Water-Cooled Stacks

Pump Source forMulti-kW DPSSL


High Power 8xx & 9xx nm CW

• Motivation:50+kW and100+kW CW Lasers forMissile Defense


• Pump Source forSolid-State Lasers(Zig-Zag-, Slab or Disk Laser)

HPDL in Defense ApplicationsConfidential Information

Very Large & Two-Dimensional StacksFEATURES

• two-dimensional arrangement (n x m)

• FAC option

• FAC/SAC option

EY-(4x8) EN(7x14)

EN(2x10)

EN(1x55)

6


803nm, 5000W, 29-bar stack, CW mode

28°C 28°C

∆λ =4.5nm (90%)


867nm, 5800W, 29-bar stack , CW mode


28°C 28°C

∆λ =4.3m(90%)


940nm, 5000W, 25-bar Stack, CW mode


25°C 25°C

∆λ =5nm (90%)


Summary on 8xx / 9xx nm stacks

Wavelength (nm)

peak efficiency

Power @ peak

efficiency (W)

max tested power (W)

Max power per bar

(W)

Spectral width (90%

power)

FA divergence

(mrad, 90%

power)

802 50.6% at 28°C

4956 4956 171 4.5 11

867 60.5% at 28°C

5506 5506 190 4.3 10

940 59.0% at 25°C

4365 4628 185 5.0 3

• Scalability of bar count per stack

• 200+W per bar

• low smile

• FAC / SAC available



Pump Sources for

Diode-PumpedAlkaline Lasers (DPAL)


Physical basics of alkali lasers

Three-level laser with small quantum defect ∆∆∆∆E/E2

Neutral alkali atom (Cs, Rb, K, Na, Li): single valence s-electron

∆∆∆∆E

E2

E1

E0

n2P3/2

n2P1/2

n2S1/2

D1 lineλλλλlaser

D2 lineλλλλpump

Fast quenching (collisional relaxation,

buffer gas: He, CH4, ethane etc.)

n: principal quantumnumber for theground configurationof alkali atoms


Physical basics of alkali lasers

Summary of transition energies and wavelengths

Laser n λpump E2-E0 E1-E0 λlaser ∆E ∆E/E2

entity (nm) (eV) (eV) (nm) (meV)

Nd3+ 808 1.5344 1.1652 1064 369.2 0.24

Yb3+ 941 1.3176 1.2038 1030 113.8 0.086

Cs 6 852 1.4546 1.3859 894.3 68.7 0.047

Rb 5 780 1.5890 1.5596 794.8 29.4 0.0185

K 4 766 1.6171 1.6099 770.1 7.2 0.0044

Na 3 589 2.1044 2.1023 589.8 2.1 0.0010

Li 2 670 1.8479 1.8479 670.1 0.04 0.00002


Motivation – Why DPALs?

• High power conversion efficiency

• High output power

• Poor beam quality

• No stress birefringence

• No beam distortions by thermal effects

• No stress fractures

• No optical damages (i.e. in laser fibers)

• Reduced thermal focussing

•

• High average output power

• High beam quality

• Single aperture power scaling

Laser diodearray

Gas (vapor) laser gainmedium

Laser outputbeam

Potential to achieve very high output powers in NIR spectral region


Motivation – Why DPALs?

Further advantages of DPALs:

• Scalability to high power (cell size, pump power)

• Low quantum defect (reduction of waste heat)

• Excellent thermal management

• Lightweight packaging

• Closed cells

Directed energy

• Laser weapons


Special requirements for DPALs

∆λ∆λ∆λ∆λ =λλλλ x cot θθθθ

Μ Μ Μ Μ fFAC

Smile contribution to thelinewidth of a 1cm bar:

e.g. ∆λ∆λ∆λ∆λ≈8GHz for a typical configuration with x = 1µm, fFAC = 9.7mm

Laser diodes:

• linewidth narrowing usingVBGs

• maybe usage of DFB lasers

• reduction of laser bar smile

Typical width of D2 absorption line: 0.01nm (or 500 MHz)

Alkali vapor medium:

• Broadening of the D2 lineby an increase of

• cell pressure and/or

• gas temperature

HPDL in Defense Applications 17DILAS Confidential

Information

0 10 20 30 40 50 60 700

50

100

150

200

250

300

350

400

450

500

outp

ut p

ower

fibe

r 40

0 µ

m N

A 0

.22

[W]

current [A]

450 W @ 400 µm NA 0.22

966 968 970 972 974 976 978 980 982 984 9860,0

0,2

0,4

0,6

0,8

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

inte

nsity

[a.u

.]

wavelength [nm]

maximum power : 456 W @ 60 A

center wavelength : 976.5 nm @ 60 A

spectral bandwidth : ∆λλλλ = 1.0 nm (95%)

number of diode bars : 12

Example of 12-bar VBG Module

966 968 970 972 974 976 978 980 982 9840,0

0,2

0,4

0,6

0,8

1,0 λpeak

= 976.5 nm

∆λ95%

= 1.0 nm

inte

nsity

[a.u

.]

wavelength [nm]

current = 50 Atemperature = 25°C


Laser diode bars for alkali laser pumping

• emitter pitch: 500 µm

• mounted on micro-channel coolers

• soft soldering

• smile (peak to valley) < 0.8 µm

FAC & SAC


Laser bars at 852nm for Cs laser pumping

• low fill factor of 30%

• 2mm cavity length

• emitter width: 150 µm

• 19 emitters per bar

25°C

40°C

20°C

Threshold current: 10.5 A

Slope efficiency: 1.23 W/A

Max. efficiency: 60.3% @ 80A / 83W

TRO @ 205A / 195W

T0 = 177 K

T1 = 200 K

Rth = 0.34 K/W


Laser bars at 780nm for Rb laser pumping



• TM polarization

20°C






• TE polarization




20°C


Laser bars at 766nm for K laser pumping



• TM polarization

20°C






• TE polarization



Max. efficiency: >56.9% @ 62A / 66W

20°C


Laser bars at 670nm for Li laser pumping


• 1.5mm cavity length

• AuSn mounting

• conduction cooled laser bars

20°C, cw

cw



Max. efficiency: 38.9% @ 35A / 28.5W

TRO @ 48A / 35.5W Rth = 1.2 K/W

qcw

Ith = 12.8 A

ηηηη = 1.24 W/A

40.2% @ 49A / 43W

20°C, qcw

pulse conditions:500µs, 1% d.c.


• scalability

• excellent thermal management

• leightweight packaging

• potential to achieve high output powers beyond the power limitations of recent solid state and fiber lasers

• 852nm (Cs) 100W/bar

• 780nm (Rb) 60W/bar

• 766nm (K) 40W/bar

• 670nm (Li) 25W/bar

• compensation of less pump power by higher alkali laser efficiencydue to smaller quantum defects


DPAL Summary

DPALs:

Ppump:

� Work is ongoing to improve materials, processes and structuresand to provide VBG-results at mentioned wavelengths

� Partial support of US Air Force is gratefully acknowledged


� 1.xxx µm High Power Diode Lasers

� selected examples


Above 1µm . . .

Motivation: „All Colors – All Packages“

• Multi-wavelengths-modules

• 1320nm – up to 120W CW fiber coupled



• 1550nm – up to 1400W QCW stacks

• 1910nm – 150W CW stacks




Multi-Bar Fiber-Coupled - P vs λλλλ


1

10

100

1000

cw

po

wer*

[W

]

wavelength [nm]

MF-400 (1x1)

IS30-400 (2x1)

IS9-400 (3x1)

IS10-400 (3x2)

IS11-400 (6x2)

400µm Ø 200µm Ø

ISXX-400 (12x2)

warranty600-690nm - 1.000h / 6 months793/1064nm - 5.000h / 1 year808-980nm - 10.000h / 2 years1210-1940nm - 2.000h / 1 year


Multi-wavelengths-Module

3-λλλλ-Version of IS9

• up to 3 different λλλλ• coupled into one fiber

• operated separately

• 1470 /1520 /1550nm

• others on request

3 barsseparately

controllableelectr. contact for:

bar 1

bar 2

bar 3


Example: 1532nm / 100W 400µm / VBG

M1F4S22-1532-100C-IS (1x6) –VBG



Example: 1550nm / 1400W / QCW

N15B-1550-1400Q-VOx.x (1x20)



Example: 1910nm / 150W / CW

E7Y-1910-150C-VS4.2 (1x10)



Example: 1950nm / 35W / 600µm / CW

M1F6S22-1950-35C-IS11x.x



Summary on >1µm HPDL

�pump wavelengths1468nm / 1532nm / 1908nm / 1938nm

�Direct Illumination / Gated Imaging

�CW and QCW (kWpeak) operation

� large wavelength-temperature-coeff.14xx / 15xx : ~0.61nm/K

19xx : ~1.2nm/K

� large linewidthmay need to compensated with VBG



Specifically Designed

Fiber Laser Pump Modules


Idea of EO-board

34

Automated Steps

• Chip mounting

• Optical alignment

• Optics mounting

• Electrical & Optical characterization

baseplate

tailoredMini bars

micro opticarea

Proprietary Information

HPDL in Defense Applications 35

FEATURES

• conduction cooled 976nm mini-bars inside

• 135W/200µm Ø/NA0.22 cladding free

• Detachable LC-SMA or SMA05Q fiber

• base plate = water cooling interface

• power meter

• fiber laser sensor

• NTC temperature sensor

• back-reflection filter

130 x 65 x 39 mm3

905 g

1 board Module (7 x 1 Mini-Bars)


opt. power: 135W @ 200µm Ø/NA0.22

cladding-free with liquid-cooled

mode-strip SMA fiber


1 board Modules for dense arrangement



1 board Module (7 x 1 Mini-Bars)


1 board Module – (7x1 Mini-Bars)


200W release

mid of 2011


cladding-free with conduction-

cooled modestrip SMA Q05

• further optimization ofMini-Bar and adaptedmicro-optics will resultin higher power withinsame footprint

• max power: 230W• max efficiency: 53%• power on dynamics: <3%


1 board Module – (7x1 Mini-Bars) – VBG


• VBG for spectral linenarrowing can beincluded

• < 10% power reductionin other words, < 2.5A current increaseto maintain power

• spectral line widthreduces to ∆λ∆λ∆λ∆λ < 1nm

965 975 985

Wavelength [nm]

In

ten

sit

y[A

.U]

Standard

0

0,2

0,4

0,6

0,8

1

965 975 985

withVBG


4 boards – Module (7x4 Mini-Bars)


600W release

end 2012



cooled modestrip QBH fiber

• based on 4 Mini-Bar base plates, with further spatial and polarization multiplexing

• QBH-Fiber200mm Ø/ NA0.22

• features- power meter- temperature sensor- back-reflection filter


4 boards - Module – (7x4 Mini-Bars)

41

• max efficiency: ~48%• max power: 775 W• QBH fiber: 200µm /NA0.22• peak wavelength: ~974 nm @ 20°C• line width (90%): ~5.1 nm




cooled mode strip QBH fiber


4 boards - Module – (7x4 Mini-Bars) – VBG

42

• Efficiency: ~ 42%• max power: ~ 675 W• power loss VBG ~ 5%• peak wavelength: ~976,7nm• line width (90%): ~0.7nm• Stable over 10–40A & 18°C–35 °C



Summary on Mini-Bar Concept


• Optimized Chip design forcost efficient beam shaping

• Automated Chip Mounting

• Automated Mounting of Chip to Board

• Concept of Electro-Optical Board

• Automated Active Alignmentand Mounting of Beam Shaping Micro Opics to Board

A part of this work was sponsored by the German Federal Ministry ofEducation and Research (BMBF) within the German national fundinginitiative “Integrated Optical Components for High Power Laser BeamSources (INLAS)”. In addition part of this work was supported withfunding from the Leadership in Fibre Laser Technology (LIFT) projectunder the 7th Framework Programme of the European Commission.


Specifically Designed

Fiber Laser Pump Modules

Light Weight„300W in 300g“

HPDL in Defense Applications 45

Prototype


o Power: 300W

o Fiber : 200 µm / NA 0.22 air-cooled SMA mode-strip

o Size : 87 x 65 x 45 mm3

(1€ coin - Ø 23.25 mm ≈≈≈≈ 0.9 inch)

o Weight : ~ 300g for light weight design

< 500g for industrial design

o Cooling : industrial water


Results for Light Weight Unit

λλλλ = 975.7 nm∆λ∆λ∆λ∆λ = 4.7 nm (90%)I = 49 A; T = 20°C

200 µm NA 0.22

o Fiber : 200 µm / NA 0.22, SMA mode-strip

o Output power : 308 W @ 50.5 A with EO-efficiency of 47 %

200 W @ 29.7 A with EO-efficiency of 56 %

o Spectral data : 975.7 nm / ∆λ∆λ∆λ∆λ = 4.7 nm (90%) @ 49 A and 20°C

o Power/Weight ratio: > 1 kW / kg


Summary on Leight Weight Unit

• FC Module

• based on DILAS Mini-Bar Concept

• 300W in 300g with 200µm/NA0.22

• Tab Water Cooling



DILAS


Germany

DILAS Diodenlaser GmbH

Galileo-Galilei-Straße 10

D-55129 Mainz-Hechtsheim

Germany

Phone: +49 (0) 6131-9226-202

Fax: +49 (0) 6131-9226-253

Email: [email protected]

www.DILAS.com

Israel

Lahat Technologies Ltd.

Head office:

15 Atir Yeda St., Kfar Saba 44643,

Tel:(972) 9-7646200

Fax:(972) 9-7646204

Branch: Teradion Ind. Zone,

20179 D.N. Misgav,

Tel:(972) 4-9990151

Fax:(972) 4-9990826

Email: [email protected]

www.lahat.co.il

Solutions for Defense Laser Applications

All Colors – All Packages


Acknowledgements

• Acknowledgements to the engineering andproduction personnel at various DILAS sites, whocontributed results and slites to this overview.

• Support from various funding programs (see notesin presentation) is also gratefully acknoweledged.


DILAS Diode Lasers used in Defense Applications March … · Alkali vapormedium: ... DPAL Summary...

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