This document summarizes the development of high-power, high-brightness laser diode pumps for fiber lasers. It describes pumps capable of outputting over 100W of continuous wave power while maintaining high efficiency and beam quality. Key points discussed include: 1. Single emitter pumps have advantages over bar stacks in cost, reliability, and performance for applications requiring kilowatt-class output. 2. New pumps achieve over 65% efficiency and output over 100W while maintaining a beam numerical aperture below 0.13. 3. Wavelength stabilized pumps provide over 50W within a 1.5nm window, suitable for pumping specific gain media. 4. 100W-class pumps demonstrate high reliability with

1. High-Brightness 9XX-nm Pumps with Wavelength Stabilization
V. Gapontsev, N. Moshegov, P. Trubenko, A. Komissarov, I. Berishev,
O. Raisky, N. Strougov, V. Chuyanov, O. Maksimov, and A. Ovtchinnikov*
IPG Photonics Corp., 50 Old Webster Rd., Oxford, MA 01540, USA
ABSTRACT
Further acceptance and fiber lasers and direct diode systems commercial success greatly depend on diodes’ availability
and cost ($/W). These two parameters should not compromise pumps’ performance and reliability. We report on two
high-brightness CW devices: high-power module launching over 100W and a pump capable of launching 50W of
wavelength-stabilized emission. Devices are based on a single emitter platform and utilize a 105 μm core diameter fiber;
radiation is confined within NA<0.13 in both designs. These hermetically sealed modules require passive cooling and
are designed to operate with ≤ 30°C diodes’ junction overheat. CW peak power efficiency is higher than 55% for both
devices. The 25-30dB isolation option (feedback protection at 10XX-nm) is optional in either package. Modules have
the industry’s smallest footprint and are perfectly suited to serve pumping fiber lasers and direct materials processing
markets.
Keywords: high-power, high-brightness, wavelength stabilized performance, high-efficiency, single emitter, pump,
diode
1. INTRODUCTION
During the last 5 years industry development efforts have moved the definition of a high power pump from ~ 3-5W to ~
50W in 105 μm fiber1,2,3,4. As a result of these efforts, clear dominance of single emitters over traditional monolithic
laser arrays has been finalized. For practical applications, such as pumping, industrial, telecom, medical, and similar, the
single emitter approach means cheaper and brighter diodes, as well as more reliable overall kilowatt-class pump engines
not based on overcomplicated and high-maintenance micro-channel cooled bar stacks. Single emitters have prevailed
not only due to obvious reason of superior performance, reliability and cost of ownership, but also due to the not so
obvious upfront cost advantage traditionally measured in $/W.
This paper focuses on IPG Photonics’ most recent developments in high-power, high-brightness single emitter
multimode pumps operating in the wavelength range of 9xx nm. These diodes are best suited for fiber laser pumping and
other applications, including direct diode systems, graphic arts, medical, special, and numerous other industries.
.
2. WAVELENGTH STABILIZED DEVICES
2.1 Further performance improvement of legacy products
IPG Photonics’ numerous products continue to utilize pumps rated to operate at 30W CW; a photo of such a pump is
presented in Figure 1. Previously, peak power efficiency for these pumps was reported at about ≤ 60% ex-fiber. Recent
improvements in sub-components quality and design, as well as ongoing chip-on-submount performance improvement,
has enabled incremental increases in power efficiency up to value greater than 65% ex-fiber CW (see Figure 2). To the
best of our knowledge, 65% electrical to optical power conversion efficiency is the highest ever reported for passively
cooled devices operating at room temperature.
*
aovtchinnikov@ipgphotonics.com; phone 1 508 373 1100; fax 1 508 373 1203; www.ipgphotonics.com
High-Power Diode Laser Technology and Applications VIII, edited by Mark S. Zediker, Proc. of SPIE
Vol. 7583, 75830A · © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi: 10.1117/12.840940
Proc. of SPIE Vol. 7583 75830A-1

2. Figure 1 Photo of the devices rated to operate at p
e power of 30W a 50-60W C
and CW.
Figure 2 Power and pow efficiency of a 97X-nm p
wer pump recorded at a heatsink t
d temperature of 25°C. Radiation is
f i
confine within the nu
ed umerical apertu of NA < 0.12.
ure
Proc. of SPIE Vol. 7583 75830A-2

3. To improve heat management we have applied the results of thermal modeling to expand the operating range of the 60W
pumps reported elsewhere1. Improved thermal performance of a 60W-device is presented in Figure 3. Temperature
insensitivity of operating characteristics significantly expands the number of possible applications of these devices
beyond conventional pumping. Wavelength insensitive applications such as direct diode, graphics, medical, and special
applications would immediately benefit from using these high-brightness (NA < 0.12) small footprint devices.
Figure 3 Set of power and power efficiency dependencies on current of a “60W” pump;
dependence of peak wavelength position on current recorded at heatsink temperature ranging from 10°C to 55°C.
2.2 High-power high-brightness wavelength stabilized pumps
There are several specific applications which would benefit from using wavelength-stabilized pumps operating at the
peak of gain media absorption. There have been few demonstrations of wavelength locking of the diode bar-based
pumps, but these devices have not materialized into commercial products due to relatively poor and inefficient
performance; the bar approach also appears to be a cost prohibitive solution due to poor locking characteristics and a
high manufacturing cost. The single emitter solution is a more promising approach to produce wavelength-stabilized
devices with high spatial and spectral brightness. In this article we report on wavelength locked devices based on the
pumps described above (see Figure 1). These devices are based on MBE-grown epitaxial material as well. This epitaxial
technique provides unique control over wavelength uniformity within run, as well as run-to-run reproducibility of
deposition process.
Figure 4 depicts the power current characteristic of a wavelength stabilized pump rated to operate at ≥ 25W power. As
one can see, this device demonstrates high spectral and spatial brightness; the numerical aperture stays below 0.12 in the
entire range of the driving current. Despite of the side-peaks emerging in lasing spectra at current of about 12A, ~ 97%
of pumping power is still contained within a 1 nm spectral window, while over 98% of the pump power is contained
within a 1.5 nm window. Peak power efficiency of this device is greater than 50%.
Proc. of SPIE Vol. 7583 75830A-3

4. Figure 4 Room temperaature power-cu
urrent and power efficiency C characteristics of a “low-p
CW power” wavele
ength
stabilized pump along w the spectra recorded at 8 10A, and 12A driving cur
d with a 8A, rrent.
Wavelength stabilized devi ices which are based on 60W pumps (see F
e W Figure 1) offer an even brigh pumping s
r hter solution.
Their rated ppower exceeds 50W while m
s maintaining a n numerical aperrture of less th 0.12. Typi
han ical power-cur
rrent and
power efficiency character ristics are presented in Figu 5 along w
ure with ex-fiber spectra recorde at different driving
ed t
currents. As one can see from this gra aph, the wave elength locking technology capability alloows for high spectral
brightness; in the entire ran of driving c
n nge currents, over 9
99% of total po
ower is contain within a 1.5 nm spectral w
ned 5 window.
Figure 6 presents the wave
elength peak p position depend
dence on drivi current for a wavelength
ing r h-locked pump rated to
operate at ≥ 50W output. The shift of the wavelength p
T e peak position is less than 0.5 nm with the d
s driving current increase
from ~ 1A t ~12A CW. Availability o such pumps adds significa flexibility in design for numerous wav
to of ant velength
specific applications.
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5. Figure 5 Ro
oom temperatu Power and P
ure Power Efficien characteris
ncy stics for “high-p
power” wavele
ength-stabilized pump
d
along with the spectra record 8A, 10A, a 12A drivin current.
e ded and ng
Figure 6 Ro
oom temperatu Power and P
ure Power Efficien characteris
ncy stics for “high-p
power” wavele
ength stabilized pump
d
along with d
dependence of p
peak waveleng position on current.
gth
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6. 3. ULTRA HI
U IGH-POWE HIGH-B
ER BRIGHTNE PUMPS
ESS S
Any type of solid state las would bene from highe
ser efit er-power highe er-brightness p
pumps. Custom demand co
mer onstantly
drives impro
ovement in these pumps’ outp Here we r
put. report on passi ively cooled p
pumps rated to operate at ove 100W
er
CW. Aside f from being the industry’s mo power effici
ost ient solution, t pump has a very small fo
this ootprint (see Figure 7),
which is an a
additional bene for most of the application
efit f ns.
Fi
igure 7 Photog
graph of a 100W CW pump h
W having a footpri less than 50 area of a bu
int 0% usiness card.
Room tempe erature perform
mance of this pa
assively cooled pump (depict in Figure 7) is presented i Figure 8. As one can
d ted ) in s
see from pow and efficie
wer ency dependen ncies of a 100WW-rated devic (with ~ 12A operating cur
ce A rrent), it can b safely
be
overdriven u to about 17A (current is lim
up A mited by powe supply in tes setup) with r
er st roll-over power at around 140
r 0-150W.
These values constitute ~50 redundancy in the therma budget of thi device, thus contributing to its high reliab
s 0% y al is o bility.
Another demmonstration of the 100W pum design’s ro
mp obustness is pr
resented in Fig raph compares thermal
gure 9. This gr
performance of 100W-rated device again a legacy pro
nst oduct which w rated to op
was perate at 30W CCW. There is virtually
ssociated with scaling up the power: junction overheat of a 100W devic is only few degrees higher than in
no penalty as e f ce
the case of t 30W-pump operated at t same drivi current. It is also worth noting that th junction ove
the p the ing he erheat in
100W pump is not that significantly different from the junction overheat pr
ps m n reviously repoorted for a 10
0W-rated
commodity p pump1.
Proc. of SPIE Vol. 7583 75830A-6

7. Figure 8 Room temp
e perature power and power eff
ficiency characteristics for a p
pump rated to o
operate at 100W
W.
Figure 9 Jun ature overheat a a function of operating cur
nction tempera as rrent for passiv cooled pum rated to op
vely mps perate at
30W and 100W CW po
d ower.
Proc. of SPIE Vol. 7583 75830A-7

8. The design of 100W rated pumps is not limited to the solid state pumping application. Direct diode systems would also
benefit from utilizing devices of this design, as well as any other non wavelength-specific applications; this applies to the
air-cooled devices as well. Demonstration of 100W devices’ ability to operate in the air-cooled applications is
demonstrated in Figure 10. In this graph, one can see a series of Power-Current and Efficiency-Current characteristics
recorded at several heatsink temperatures. As one can conclude from analyzing these graphs, applications based on
limited passive heatsinking solutions, air-cooled devices, or portable designs can clearly benefit from using these high-
power, high-brightness sources of light power. All of the above, in combination with low cost ($/W), low weight, low
profile, small footprint, and high brightness (ex-fiber NA ≤ 0.13), ensure wide utilization of these devices in various
industrial, medical, and special applications.
Figure 10 Set of CW power-current and power efficiency versus current characteristics recorded at several heatsink
temperatures, alongside with peak wavelength versus current dependencies.
4. CONCLUSIONS
High-power, high-brightness pumps continue to be a very dynamic and rapidly evolving sector of the laser industry
mostly driven by fiber laser requirements and progress. Recent developments in the single emitter pumping platform
provide advantages ensuring further domination of fiber lasers over any other alternative solution. Other applications,
such as direct diode systems and special applications, can immediately benefit from utilizing these most recent
developments.
Proc. of SPIE Vol. 7583 75830A-8

9. 5. ACKNOWLEDEGEMENTS
The authors would like to thank their co-workers at IPG Laser (Germany); without their contribution and on-going
support, this work would not be possible.
REFERENCES
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Kuang G.; Maksimov O.; Ovtchinnikov A., “High-brightness fiber coupled pumps”, SPIE Proceedings Vol. 7198,
(2009)
[2] Qiu X. Dai Y.; Au M.; Guo J.; Wong V.; Rossin V.; Venables D.; Skidmore J.; Zucker E., “A high power high-
brightness multi-single-emitter laser pump platform”, SPIE Proceedings Vol. 7198, (2009)
[3] Pawlik S.; Guarino A.; Matuschek N.; Bättig R.; Arlt S.; Lu D.; Zayer N.; Greatrex J.; Sverdlov B.; Valk B.;
Lichtenstein N., “Improved brightness on broad-area single emitter (BASE) modules”, SPIE Proceedings Vol. 7198,
(2009)
[4] Leisher P.; Price K.; Karlsen S.; Balsley D.; Newman D.; Martinsen R.; Patterson S., “High-performance
wavelength-locked diode lasers”, SPIE Proceedings Vol. 7198, (2009)
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