Special IssueLaser Processing for Copper

Development of the High-Power Blue Laser Diode Moduleand its Laser System
Naoki Hayamizu*, Hajime Mori *With the goal of applying blue lasers to the metal processing, we have developed a high-power blue diode module in cooperation with Nichia Corporation.
Nichia Corporation has made a blue laser diode (blue LD) which outputs the highest opticalpower in the world enclosed in a small-sized package and Furukawa Electric has modularized it
based on the technology acquired in developing an infrared laser diode module (IR LDM) applied
to fiber lasers. As a result, we have successfully developed the blue laser diode module (blueLDM) which generates an optical output power of 185 W in average through an optical fiber ofapproximately 100 μm in core diameter and has a high reliability with no decrease in the optical
output power even after a continuous operation of 1,000 hours and exceeding.
We have built a Direct Diode Laser (DDL) by connecting the blue LDM mentioned above with acontrol circuit and a drive circuit and have successfully developed the Blue-IR Hybrid Laser
System “BRACE” by combining it with an IR fiber laser.

ABSTRACTINTRODUCTION
1.1.INTRODUCTION
Most recently, momentum to regulate selling new gasoline
vehicles has risen rapidly under the policies of various
governments to prevent the global climate change andrealize the sustainable society. Therefore, replacement toElectrified Vehicles (xEV) including Hybrid Electric
Vehicles is more promoted from since. It is forecasted that
32% of vehicles will be replaced to xEV in the 2030s and
51% in the 2040s and this trend may be further accelerated. It is important to reduce the production cost and provide xEV at a lower price at similar level as that of today’s
gasoline vehicles to promote the widespread of xEV in thesociety. A lot of copper is used in motors, inverters andlithium-ion batteries which are core components for xEV.
Processing copper such as welding motor magnet wires,
welding bus bars or welding battery foil is highly required
for each of them. We expect more demand for the laser
processing, which can process copper free from contact,by higher speed, and in higher accuracy.
However, it is known that to process copper with aninfrared fiber laser is difficult, which is already in the market by Furukawa Electric for laser processing.
We have formed a business alliance with Nichia
Corporation and have developed a blue LDM targeting at
the optical output power of 100 W or more through an
optical fiber of approximately 100 μm in core diameter. As
shown in a special paper “Development of High-Power*

Advanced Laser Development Project Team, Incubator Dept.,
R&D Division

Blue Laser Diodes” written by Dr. Nagahama, of Nichia
Corporation, Nichia Corporation has developed a blue LD
which generates the optical output power of 11.2 W, theworld highest output among any blue LDs with one emitter and has also developed a small-sized package
enclosing the blue LD: Side Lead Package (SLP).
Furthermore, Furukawa Electric has developed the blue
LDM equipped with this SLP by applying its design technologies and production technologies of the infrared laser
diode module (IR-LDM) applied to the IR fiber lasers ofFurukawa Electric.

STRUCTURE
HIGH-POWERBLUE
2.2.STRUCTURE
OFOF
HIGH-POWER
BLUE LDMLDM
The structure of an IR-LDM is shown in Figure 11). In thismethod, infrared laser diodes (IR-LDs) are arranged in aform of stairs and the optical output power of each IR-LD
is input into an optical fiber through optical parts such aslenses and mirrors to reach higher output. As for the blue
LDM, this part of the IR-LD is replaced with the SLP, andFAC

SAC

MirrorLDFFLhSFL

FiberFigure 1 Structural drawing of IR-LDM.

Furukawa Electric Review, No. 52 2021

21200250
Optical output power

200Voltage

150

150
100
100
505000123456789 10 11Forward voltage (V)optical parts and the structure are optimized to the SLP.
The temperature of our IR-LDM is controlled by coolingits package as a whole through an external heat sink.
However, cooling through an external heat sink is insufficient for the blue LD, because the amount of the exhaust
heat from the blue LD is as much as approximately double of that of our IR-LD as one of its characteristic properties. It is desirable for the blue LDM to cool each of its
SLPs efficiently and uniformly to realize higher optical
output power, more stable performance and higher reliability. For this purpose, as shown in Figure 2, we adopted such an integrated base plate with a water-coolingheat sink so that a water channel is formed along with theslope of stairs 2).

Optical output power from the ﬁber end (W)Development of the High-Power Blue Laser Diode Module and its Laser System0Driving current (A)Figure 3 Typical L- I and V-I characteristics of the blue LDM.

SLP

1.2

Intensity

1.0

Water holes

0.8
0.6
0.4
0.2

Figure 2 Structural drawing of cooling system for SLP.

0.0
450

455460465470

Wavelength (nm)3.CHARACTERISTICSOFOFTHE HIGH-POW3. CHARACTERISTICS
ERBLUELDM
THE HIGH-POWER BLUE LDM
Figure 3 shows typical characteristics of optical outputpower vs input current “L- I characteristics” and voltage
vs current “V-I characteristics” of the designed high-output blue LDM and was made based on the technologies
mentioned above. Setting the temperature of coolingwater at 25°C, the measurement was carried out under
the Continuous Wave (CW) driving. As a result, the fibercore of approximately 100 μm in diameter has achieved
the optical output power of 185 W with a rated driving
current of 8.5 A and 220 W with 10.5 A which was the endof life current. These are the highest-class optical output
power density in the world output through a fiber core of
approximately 100 μm in diameter. Further, the typicalwave spectrum of the blue LDM is shown in Figure 4. The
mean wavelength is approximately 462 nm and is almost
same as that measured at SLP, which is indicating thatthe blue LDM is sufficiently cooled by the integrated baseplate with a water-cooling heat sink.

Figure 4 Typical wavelength spectrum of the blue LDM.

RELIABILITY
THE
HIGH-POWER
4.4.RELIABILITY
OFOF
THE
HIGH-POWER
BLUELDMLDMBLUEThe summarized result of aging test with 5 samples ofblue LMDs under the end of life current: 10.5 A is shownin Figure 5. Excellent reliability of our blue LDM which is afusion of exceptionally reliable blue LDs of Nichia
Corporation and the LDM manufacturing technology ofFurukawa Electric is shown as the changing rate of optical output power from the fiber end is no more than 1%even after 1000-hour aging.
Further, the summarized result of heat shock test andhigh-temperature storage test with 5 samples, which areexamples of the reliability test is shown in Figure 6. In theheat shock test, 1 cycle consists of temperature change
from -20°C to +70°C and from +70°C to -20°C. After
exposing to the temperature load as many as 100 cycles,
the optical output power changed only by ±4% or less toshow a good sufficient result. In the high temperaturestorage test, the optical output power changed only by±1% or less after exposing for 500 hours in the environment of 70°C which is high enough against 50°C of specified storage temperature. Considering these results, wethink we have developed a blue LDM reliable enough forindustrial applications such as copper processing.
Furukawa Electric Review, No. 52 2021

22Changing rate of optical output power (%)@ 10.5 A

Development of the High-Power Blue Laser Diode Module and its Laser System

20BLUE-IR
HYBRIDLASER
SYSTEM
5.5.BLUE-IR
HYBRIDLASER
SYSTEM“BRACE”“BRACE”

151050-5-10-15-200500

1500

1000

We have built a blue DDL by connecting the blue laser
module mentioned above with a control circuit and adrive circuit and have successfully developed the Blue-IRHybrid Laser System “BRACE” by combining it with an
IR fiber laser. The shape of the apparatus is shown inFigure 7 and the output characteristics of the blue laser
and the IR laser is shown in Figure 8. Output power of150 W or more is gained for the blue laser and 1 kW or
more for the IR laser.

Elapsed time (h)Changing rate of optical output power (%)@ 8.5 A

Figure 5 Aging test result of the blue LDM.

Heat shock test (-20/+70℃)

20151050-5-10-15-200204060

80

Figure 7 Blue-IR hybrid laser “BRACE”.

10020151050-5-101600

210

14001801200

150100012080090600
Blue laser
IR laser60300020406080

400
200
1000Output power settings of BRACE (%)

Figure 8 Typical L-I characteristics of BRACE.

-15-20240

IR laser optical output power (W)High temperature storage test (70℃)

Blue laser optical output power (W)Changing rate of optical output power (%)@ 8.5 A

Number of temperature cycle (cycles)

0100200300

400500Elapsed time (h)Figure 6 Heat shock test and high temperature storage test
results of the blue LDM.

SUMMARYAND
OUTLOOKFORFORTHE
6.6.SUMMARYANDANAN
OUTLOOKTHE FUTURE
FUTUREWith the goal of applying blue lasers to the metal processing, we have developed a high-power blue diodemodule in collaboration with Nichia Corporation. We integrated the SLP developed by Nichia Corporation into theLDM applying our technology of IR-LDM of Furukawa
Electric and have developed the optimized LDM. As aresult, we have successfully developed the blue laser
diode module “blue LDM” which outputs an average optiFurukawa Electric Review, No. 52 2021

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Development of the High-Power Blue Laser Diode Module and its Laser Systemcal power of 185 W at the rated driving condition throughan optical fiber of approximately 100 μm in core diameterand furthermore, has a high reliability with change of only
approximately 1% or less of the optical output power
even after continuous operation with as high as 220 W
output for 1,000 hours or longer. We have built an blue
DDL by connecting the developed blue laser module witha control circuit and other circuits and combined it withan IR fiber laser and successfully launched the Blue-IRHybrid Laser “BRACE” into market.
From now on, Nichia Corporation will concentrate itsefforts to develop further high-output blue LD. And Nichia
Corporation and Furukawa Electric are planning toimprove the optical coupling efficiency from LD to opticalfiber furthermore and will develop a blue LDM which outputs 300 W or more from an optical fiber.

REFERENCES
1) Y. Ishige, E. Kaji, E. Katayama, Y. Ohki, G. Gajdátsy, A. Cserteg:“120W, NA_0.15 Fiber Coupled LD module with 125-µm clad /NA 0.22 fiber by spatial coupling method”, Proc. of SPIE, 10514,(2018), 105140M.
2) Y. Ishige, H. Hashimoto, N. Hayamizu, N. Matsumoto, F. Nishino,
M. Kaneko, H. Nasu, G. Gajdátsy, A. Cserteg, K. Jahn, T. Hirao,
H. Matsuo, R. Konishi: “Blue laser-assisted kW-class CW NIR
fiber laser system for high-quality copper welding”, Proc. of SPIE
11668 (2021) 116680M.

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