1-kW, All-Glass Tm:fiber Laser

SPIE Photonics West 2010: LASEFiber Lasers VII: Technology, Systems, and

Applications, Conference 7580Session 16: Late-Breaking News

January 28, 2010

Thomas Ehrenreich, Ryan Leveille, Imtiaz Majid, and Kanishka Tankala

Nufern, Inc. Glen Rines and Peter Moulton

Q-Peak, Inc.

Outline

• Review of prior results• Components• Laser results• Summary

Support: HEL/JTOContract Number: FA9451-08-D-0199/0002

Early Q-Peak results scaling to 300 W, single-mode

0

25

50

75

100

125

150

175

200

225

250

275

300

325

0 50 100 150 200 250 300 350 400 450 500 550 600

Launched pump power (W)

Out

put p

ower

(W)

LMA HI2 fiber data conduction cooled, new clampsLinear fitLMA HI2 fiber data conduction cooledLinear fitLMA HI2 fiber data water cooledLinear fit

59.1% slope

61.8% slope

301 W

64.5% slope

powermeter

Pump Laser A

Pump Laser B

focusinghead

Meniscus2.5-cm R concave surface

HR at 2050 nmHT at 790 nm

Dichroicmirror

HR at 2050 nmHT at 790 nm

clamp

Heat sink

clamp

Active fiber coil

focusinghead

2050 nm output

793-nm pump400-um, 0.2 NAfiber delivery

Single-ended pump

powermeter

Pump Laser A

Pump Laser B

focusinghead

Meniscus2.5-cm R concave surface

HR at 2050 nmHT at 790 nm

Dichroicmirror

HR at 2050 nmHT at 790 nm

clamp

Heat sink

clamp

Active fiber coil

focusinghead

2050 nm output

793-nm pump400-um, 0.2 NAfiber delivery

Single-ended pump

Gain fiber: 5-m long, 3-m undoped ends (2)Core: 25 m in diameter, NA: 0.08.

Pump cladding: 400-m in diameter

Record powers (885 W) with bigger pumps and spectacular damage

powermeter #1

Pump Laser 1

Pump Laser 2

focusinghead

Dichroicmirror(2)

HR at 2050 nmHT at 790 nm

clamp

Water bath

clamp

Active fiber coil

focusinghead

2050 nm outputs

793-nm pump1000-um, 0.2 NA

fiber delivery

powermeter #2

powermeter #1

Pump Laser 1

Pump Laser 2

focusinghead

focusinghead

Dichroicmirror(2)

HR at 2050 nmHT at 790 nm

clamp

Water bath

clamp

Active fiber coil

focusinghead

focusinghead

2050 nm outputs

793-nm pump1000-um, 0.2 NA

fiber delivery

powermeter #2

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Launched Power (W)

Tota

l Out

put P

ower

(W)

Fiber 0Fiber 1, test 1Fiber 1, test 2Fiber 1, test 3Fiber 2, test 1

53.7% slope

Would have made it here?

NGAS 600-W Single-frequency MOPA (PW 2009)

Gregory D. Goodno, Lewis D. Book, and Joshua E. Rothenberg

IPG 415-W all-glass result (CLEO Europe 2007)

The laser setup was consist of an 8 meters of low concentration Tm-doped fiber with core diameter of ~20 mm and a pair of fiber Bragg gratings (FBG), fusion spliced with an active fiber, forming a laser cavity. The output of the Tm fiber laser was terminated by a single-mode fiber with mode field diameter (MFD) of LP01 mode and wavelength of the cutoff of LP11 equal to 14 mm and 1450 nm respectively. The reflectivity of output FBG was ~1dB. The double clad Tm fiber was end-pumped to the cladding through the strong FBG by pump fiber assembly consisting of 18 40W CW Er fiber lasers at 1567nm. The total in-fiber power of this pump assembly output more than 720W CW. The 1567nm pumping of Tm fibers compare to 793nm pumping advantage in no up-conversion processes that leads to fiber degradation due to photodarkening.

M. Meleshkevich, N. Platonov, D. Gapontsev, A. Drozhzhin, V.Sergeev, V.Gapontsev

Outline

• Review of prior results• Components• Laser results• Summary

Components for all-glass laser – single stage

(6+1) to 1Co-propagatingCombiner

Tm-doped 20/400 fiber10-m length

150-W fiber-coupledpump modules at 79X nm

FBG oscillator50 W at 2041 nm

Angled end-capon fiber

Using DILAS “second generation” fiber-coupled diodes

DILAS modules have nearly 40% electrical-optical conversion

0

20

40

60

80

100

120

140

160

180

0 50 100 150 200 250 300 350 400 450

Electrical power (W)

Opt

ical

Pow

er (W

)

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Con

vers

ion

effic

ienc

y

Outline

• Review of prior results• Components• Laser results• Summary

Results from single stage: >500 W

0

100

200

300

400

500

600

0 100 200 300 400 500 600 700 800Pump power (W)

MO

PA

out

put p

ower

(W)

Fiber #1Fiber #261.6% slope efficiency

Two-stage power amplifier

MO

Pumps (6) Pumps (6)

Tm:fiber Tm:fiber

(6+1)x1pumpcoupler

(6+1)x1pumpcoupler

Claddingstripper

Output

MO

Pumps (6) Pumps (6)

Tm:fiber Tm:fiber

(6+1)x1pumpcoupler

(6+1)x1pumpcoupler

Claddingstripper

Output

MO

50 Watts at 2045-nm

1st Stage

12m LMA-TDF-20/400 active fiber

2nd Stage

12m LMA-TDF-20/400 active fiber

> 1 kW of power output at 2045 nm

0

200

400

600

800

1000

1200

0 500 1000 1500 2000

Pump Power (W)

Sign

al P

ower

(W)

53.2% slope

Summary

• High-power, “all-glass” operation of a 79X-nm pumped Tm:fiber laser has been made possible by development of:– High-brightness, fiber-coupled pump lasers– Fiber-based, (6+1):1 pump-coupling optics

• To date, power levels achieved are:– > 500 W with six pump lasers– > 1 kW with twelve pump lasers

• Based on the fibers used, the results represent single-mode operation at 2045 nm and the highest cw power level (to our knowledge) ever generated in this wavelength range

• Improvements are possible in all of the components, leading to higher powers and efficiencies

• Substantial further scaling of this approach will rely on development of higher-brightness pump lasers