High-power single emitters and laser bars find several growing industrial applications such as materials processing. A
steady increase in efficiency and output power is needed to conquer new markets. The development of high-end diode
lasers usually starts with the development of the epitaxial structure. Therefore, simulations have been performed before
the optimized layer structures have been tested using broad area (BA) lasers. Single emitter laser diodes are needed for
fiber coupling with a minimal loss of light. We developed such emitters with high output powers at a small far field
angle showing output powers of more than 20 W around 940 nm. The high-quality laser bars available at JENOPTIK
have been improved and extended to new wavelength ranges. At the lower end, laser bars have been developed around
and below 800 nm. At the higher end, design parameters have been optimized for 1060 nm emission wavelength.
Laser diodes and laser bars for the high-volume wavelength ranges at 808 nm and 940 nm are available in optimized
design and high quality. However, a lot of other wavelengths in the NIR are needed for specialized applications also
requiring high stability, reliability and a good efficiency with a good beam quality. An efficient adaptation of the laser
diode design to optimize the laser performance at the customized wavelength is highly desirable. At JENOPTIK Diode
Lab (JDL) we therefore focus on a flexible and competitive laser diode design resulting in a high output power and a
high efficiency at reasonable production costs. Starting from excellent laser bars at 808 nm and 940 nm laser bars with
emission wavelengths around 790 nm, 830 nm, 880nm (cw) and 940 nm (pulsed operation) are developed. For 792 nm a
maximum output power of 90 W and an efficiency of 55 % has been achieved with an expected lifetime of more than
15000 hours. At 825 nm a maximum efficiency of 60 % and 60 W output power for more than 20.000 h with a high
degree of polarization can be presented. Changing the quantum well material for 885 nm the output power reaches 125W
with 63% efficiency also for more than 25.000 hours. Laser bars for pulsed applications (quasi-cw) at 940 nm result in an
output power of 500 W with an efficiency of 60 %.
Lasers for marking, direct application laser systems as well as high power solid state lasers require highly reliable, high
efficient and low cost laser diodes. Especially fiber lasers and direct diode systems have additionally the need for high
brightness. For a very long time either single emitter solutions with low brightness and costs or beam shaped bar
solutions with high brightness and high costs served those needs. Since roughly 2 years multiple single emitter solution
are more and more penetrating the market showing a high potential for serving all needs of a broad customer base.
Based on the 50W product introduced by the middle of 2009 we would like to show the design which is based on
qualified and highly stable single emitters.
The industry of laser marking, direct application and solid state laser pumping requires highly reliable and highly
efficient laser diodes. In general, all applications demand improved brightness and temperature stability, and this by
decreasing costs per watt. Instead of increasing the cavity length, we demonstrate in this paper an increase of power
with standard cavity length with a clear focus of cost reduction and high efficiency. Improvements in the semiconductor
material and packaging enable higher power and higher operation temperature. This technology raised the efficiency by
6 % of 808 nm bar with 50 % filling factor and a resonator length of 1.5 mm.
Now, passively cooled diode lasers have reached nearly the performance of actively cooled ones. With this new design
new fiber coupling modules with high brightness and high operation temperature for air cooled systems can be
achieved.
Broad area diode laser and diode laser bars are the most efficient light sources. In comparison to solid state laser or gas
laser systems the over all beam quality of the diode laser is poor. Thus most application of diode laser bars is high
efficient pumping of solid state lasers converting the beam quality and scaling the power of laser systems within the kW
range. The pump efficiency and the beam coupling efficiency of the diode laser pumped systems has to be increased to
meet the increasing laser market demands for reduced costs. JENOPTIK Diode Lab GmbH (JDL) has optimized their
high power brilliance bars to enable reliable high power operation especially, for the 9xx nm wavelength range and low
far field divergences. Superior reliability with long operation time of 13,000 hours and high power operation of 200 W
are demonstrated for high power bars high filling factor mounted on passively cooled heat sinks. Smaller far field
divergence at high power levels requires longer cavity length and higher efficiencies in the beam coupling needs
requires lower filling factors. The new high brilliance bars and arrays with 20% filling factor are showing high power
operation up to 95 W and a slow axis beam divergence of less than 8° (95% power content).
KEYWORDS: Semiconductor lasers, High power lasers, High power diode lasers, Laser systems engineering, Fiber lasers, Nd:YAG lasers, Reliability, Waveguides, Diodes
The strong increasing laser market has ongoing demands to reduce the costs of diode laser pumped systems. For that
reason JENOPTIK Diode Lab GmbH (JDL) optimized the bar brilliance (small vertical far field divergence) and bar
efficiency (higher optical power operation) with respect to the pump applications. High efficiency reduces the costs for
mounting and cooling and high brilliance increases the coupling efficiency. Both are carefully adjusted in the 9xx nm -
high power diode laser bars for pump applications in disc- and fiber lasers. Based on low loss waveguide structures high
brilliance bars with 19° fast axis beam divergence (FWHM) with 58 % maximum efficiency and 27° fast axis beam
divergence (FWHM) with 62 % maximum efficiency are developed. Mounted on conductive cooled heat sinks high
power operation with lifetime > 20.000 hours at 120 W output power level (50 % filling factor bars) and 80W (20 %
filling factor bars) is demonstrated.
808nm bars used as pump sources for Nd:YAG solid state lasers are still dominating in the market. With respect to the
demands on high reliability at high power operation current results of a 100 W high power life time test are showing
more than 9000 hour operation time for passively cooled packaged high efficiency 50 % filling factor bars.
Measurement of the COMD-level after this hard pulse life time test demonstrates very high power levels with no
significant droop in COMD-power level. This confirms the high facet stability of JDL's facet technology.
New high power diode laser bars with wavelength of 825 nm and 885 nm are still under development and first results
are presented.
Improvements of laser diode bar efficiency and mounting technology have boosted output powers of passively cooled
diode lasers beyond the 100W cw limit. After an introduction about reliablity statements and reliability assessment, the
performance increase by technology improvements is documented in current-step failure discrimination tests. Electro-optical
parameters of improved diode lasers are subsequently presented in detail as well as the results of lifetime tests at
different powers and in different operation modes - steady-state and repetitive/intermittent ("hard pulse") cw operation.
Based on a well established technology for continuous-wave (cw) diode lasers, further development and optimization
lead to high performance laser bars for quasi-continuous-wave (qcw) operation suitable for pumping applications.
Mounted on standard heat sinks, these 808nm laser bars exhibit more than 300W (400W) qcw output power with 50%
(75%) filling factors. Reliability tests of these bars are running at >200W. Several GShots at 2, 4 and 10% duty cycle
(d.c.) were already achieved.
With this high performance qcw laser bars, passively cooled laser stacks were developed and tested using a new design
compatible to high power operation. Thermal expansion matched materials and hard solder techniques allow reliable
operation, even under rough environmental conditions. Output powers of 2.5kW (>300W per bar) were demonstrated
from a stack with 8 bars. After environmental tests (vibration and thermal cycles), an ongoing life test exhibits more than
2.5GShots with 1.6kW (~200W per bar) at 4% duty cycle.
There are strong demands at the market to increase power and reliability for 808 nm diode laser bars. Responding to this
JENOPTIK Diode Lab GmbH developed high performance 808 nm diode laser bars in the AlGaAs/GaAs material
system with special emphasis to high power operation and long term stability. Optimization of the epitaxy structure and
improvements in the diode laser bar design results in very high slope efficiency of >1.2 W/A, low threshold current and
small beam divergence in slow axis direction. Including low serial resistance the overall wall plug efficiency is up to
65% for our 20%, 30% and 50% filling factor 10 mm diode laser bars.
With the JENOPTIK Diode Lab cleaving and coating technique the maximum output power is 205 W in CW operation
and 377 W in QCW operation (200 &mgr;s, 2% duty cycle) for bars with 50% filling factor.
These bars mounted on micro channel cooled package are showing a very high reliability of >15.000 h. Mounted on
conductive cooled package high power operation at 100 W is demonstrated for more than 5000h.
KEYWORDS: Semiconductor lasers, Reliability, Diodes, Resonators, High power lasers, Pulsed laser operation, Continuous wave operation, Electro optics, Near field optics
We report present advantages of high power 9xxnm diode laser bars for pumping of disc laser and especially for
pumping fibre lasers and amplifiers.
The strong demand for reduce system costs needs to have a good compromise in improved diode laser power, conversion
efficiency, reliability and beam quality leading to simplified system designs. Basis of the new generation for the 9xxnm
laser diode bars at JENOPTIK Diode Lab is a low loss wave guide AlGaAs - structure with low vertical far field angle of
27° (FWHM). Recently we demonstrate an output power in excess of 500W in CW operation from a diode laser bar with
50% filling factor and 3.0mm cavity length. This record was possible due to high power conversion efficiency of >68 %,
optimised facet coating technology and an excellent active cooling. New results on conductive cooled high brightness
laser bars of 20% filling factor with special emphasis to the needs of high efficiency fibre coupling will be presented.
Lifetime tests under long pulse conditions have demonstrated a very high reliability for 120 W laser bars with 50 %
filling factor and for 60 W laser bars with 20 % and 30 % filling factor.
The new packaging technology from JENOPTIK Laserdiode GmbH and the new chip technology from JENOPTIK
Diode Lab GmbH increases the output power, the quality and durability of new broad area lasers.
Tests with different pulse widths and duty cycles have been conducted. A maximum linear power density of
213mW/&mgr;m has been found for 808nm and 980nm laser, limited by thermal rollover. The tests were performed for duty
cycles from 0.1% to 5% and pulse widths of 50&mgr;s and 100&mgr;m. Over 32W output power was reached for 150&mgr;m emitter
at a 0.1 % duty cycle and 50&mgr;s pulse length. With the new diode laser technology 10mm bars with a 44% filling factor
were produced. These laser bars, mounted on micro channel coolers, reached a maximum output power of 1000W. To
our knowledge this is the highest power reported up to now for 980nm material with 100&mgr;s pulses and 0.1% duty cycle.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.