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Super High Power Industrial Laser Diode
Achieves 1 kW, the Industry’s Highest Level
High Power Industrial Laser Stack Technology |
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High output power:
1 kW |
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High optical power
density (space-saving device) |
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High reliability |
Recently, lasers have become widely used
for cutting, welding, and marking in the
industrial machining area. Of these, the
YAG laser, which is used for cutting and
welding, becomes the mainstream in laser
machining in place of the CO2 laser,
and the developments in this area have
been remarkable. Higher efficiency and
reliability from the standpoints of low cost
and reduced environmental burden. Market
stream changes from lamp pumped
YAG lasers to laser diodes pumped YAG
lasers, and furthermore laser diodes are
used directly in machining applications.
Therefore, to respond to this outlook for
the laser machining field, Sony is applying
its high-power laser diode technologies
proven in optical disc laser diodes to
promote the development of super high
power laser diodes.
Sony has now arrived at the point where
it can announce a stack laser with the
industry’s highest level of power. In this
article, we introduce this technology from
three viewpoints: high power, high optical
power density, and high reliability. |
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Stacking Technology = High Power Laser |
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The optical output of laser diodes used in
DVD recording is around 150 mW. A
stack laser with an optical output of 1 kW
would be about 6600 times that power.
This is such an enormous amount of energy
that it defies the imagination.
Up to now, Sony has succeeded in
developing a laser diode product (the
SLD433S4) with an optical output of 60
W. It has now become possible, by applying
Sony’s engineering ingenuity to
that technology, to increase that 60 W
optical power to 1000 W.
This ‘engineering ingenuity’ consists of
a ‘stacking technology’ that layers lasers
on top of one another.
At the same time as providing highly efficient
cooling, the water-cooled heat sink
used in the SLD432S4 and SLD433S4
has the feature that it is extremely thin.
Furthermore, since it has a structure in
which the cooling water flows directly
inside the heat sink, it provides a high
degree of design flexibility and by ingenious
design of water path, allows ‘stacking’,
that is, direct stacking of heat sinks.
By stacking 25 layers of 40 W power
output lasers, Sony was able to create a
practical module, a single one of which
provides a 1 kW optical power output.
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Making the Heat Sink Thin
= High Optical Power Density |
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Unlike the light from an incandescent
lamp, the light from a laser diode has the
feature that a high optical power can be
acquired from a smaller area. It has now
become possible to mount laser diode
chips even closer together using stacking
technology, and thus to take even greater
advantage of this feature of laser diodes.
This also has the large advantage of saving
space.
The development effort described here
aimed at reducing the stack laser's emission
pitch (the spacing between emission
points when the laser diode are stacked)
to under 2 mm. As we mentioned in the
previous section on stacking technology,
the water-cooled heat sink features a high
degree of flexibility in the structural design
and also provides powerful cooling.
By performing simulations and revising
the design, we succeeded in reducing the
thickness of the heat sink while retaining
the previous cooling capacity without
change. This allowed us to achieve a
stacking pitch of 1.9 mm, thus achieving
our goal.
A device with 25 layers and a stack pitch
of 1.9 mm has a height of 47.5 mm (a
width of 10 mm and a height of 47.5 mm)
and achieves the high optical power density
of 211 W/cm2 as its optical power per
unit area. |
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High Reliability |
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| When developing industrial lasers, the
most important issue is the reliability. By
adopting the stripe structure from the
SLD430 Series, which are attractive
products due to their high reliability and
low operating current, and by adopting
water-cooled heat sink technology that
can provide high reliability even at the 60
W power level, we were able to assure
high reliability in this stack array laser
module. |
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See
all articles with figures and tables.  |
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Vol.42 |
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