A new 100μm aperture, 920nm laser diode chip was developed to improve fiber coupling efficiency and reliability. These chips have been assembled into single-emitter and multi-emitter packages with 105μm diameter fiber-coupled output. The single-emitter package is rated for 12W operation, while the multi-emitter package is rated at 140W. Power conversion efficiency is 50%. Over one year of accelerated active life testing has been completed along with a suite of passive, environmental qualification tests. These pumps have been integrated into 2kW, 4kW, and 6kW fiber laser engines that demonstrate excellent brightness, efficiency, and sheet metal cutting quality and speed.
Hongbo Yu, Dahv A. Kliner, Kai-Hsiu Liao, Jeff Segall, Martin Muendel, James Morehead, Jane Shen, Matt Kutsuris, Johnny Luu, Justin Franke, Kelvin Nguyen, Dave Woods, Fred Vance, David Vecht, David Meng, Richard Duesterberg, Lei Xu, Jay Skidmore, Matthew Peters, Nicolas Guerin, James Guo, Jane Cheng, Jihua Du, Brad Johnson, Dongliang Yin, Allen Hsieh, Peter Cheng, Abdullah Demir, Jason Cai, Rupa Gurram, Kong-Weng Lee, Reddy Raju, Daniel Zou, Raman Srinivasan, Mandeep Saini, Laura Zavala, Victor Rossin, Erik Zucker, Hiroaki Ishiguro, Hiroshi Sako
We have demonstrated a monolithic (fully fused), 1.2-kW, Yb-doped fiber laser with near-single-mode beam quality.
This laser employs a new generation of high-brightness, fiber-coupled pump sources based on spatially multiplexed
single emitters, with each pump providing 100 W at 915 nm within 0.15 NA from a standard 105/125 μm fiber. The
fiber laser is end pumped through the high-reflector FBG using a 19:1 fused-fiber pump combiner, eliminating the need
for pump/signal combiners. The output wavelength is 1080 nm, with a linewidth of < 0.5 nm FWHM. A peak power of
1.5 kW was reached in modulated operation (1-ms pulse duration) with M2 < 1.2.
Richard Duesterberg, Lei Xu, Jay Skidmore, James Guo, Jane Cheng, Jihua Du, Brad Johnson, David Vecht, Nicolas Guerin, Benlih Huang, Dongliang Yin, Peter Cheng, Reddy Raju, Kong Weng Lee, Jason Cai, Victor Rossin, Erik Zucker
We report results of a spatially-multiplexed broad area laser diode platform designed for efficient pumping of fiber lasers
or direct-diode systems. Optical output power in excess of 100W from a 105μm core, 0.15NA fiber is demonstrated with
high coupling efficiency. The compact form factor and low thermal resistance enable tight packing densities needed for
kW-class fiber laser systems. Broad area laser diodes have been optimized to reduce near- and far-field performance and
prevent blooming without sacrificing other electro-optic parameters. With proper lens optimization this produces ~5%
increase in coupling / wall plug efficiency for our design. In addition to performance characteristics, an update on long
term reliability testing of 9XX nm broad area laser diode is provided that continues to show no wear out under high
acceleration. Under nominal operating conditions of 12W ex-facet power at 25C, the diode mean time to failure (MTTF)
is forecast to be ~ 480 kh.
KEYWORDS: Thermoelectric materials, Performance modeling, Sensors, Finite element methods, Semiconductor lasers, 3D modeling, Semiconductors, Manufacturing, Data modeling, High power lasers
High-power single-emitter semiconductor lasers may dissipate up to several Watts heat load during operation. The heat
may be generated from a narrow stripe, as low as a few microns in width by several millimeters in length.
Thermoelectric Coolers (TEC) are widely deployed to control the laser junction temperature in single-emitter
semiconductor-laser packages. TEC manufacturers supply performance curves under the assumption of uniform heat
load applied to the cold plate. In reality, the heat will spread laterally across the cold plate creating a temperature
gradient across the couples. Consequently, the actual performance of the TEC may be significantly degraded as
compared to that predicted from the manufacturer's guidelines. A quantitative analysis that includes these deviations is
necessary to properly size the TEC and optimize the package design. This paper provides a simple method for modeling
the TEC performance parameters on concentrated heat loads using commercially-available FEA software. Experimental
data of TEC cooled single-emitter laser packages will also be presented that corroborate the results of our model.
We present kW QCW vertical and horizontal arrays composed of 200W bars (peak power) at 8xxnm wavelength. We
also present an unique Bar-on-Submount design using the electrically insulating submounts, which can provide a
platform for simple and flexible horizontal array construction. The p-n junction temperature of the arrays under QCW
operation is modeled with FEA software, as well as measured in this research. Updated reliability test results for these
kW arrays will be also reported. As the examples, we present the performance of the vertical arrays with > 57% Wall-Plug-Efficiency and the horizontal arrays with < 23 degree fast axis divergence (FWHM), both with 808nm wavelength.
The available wavelength for such arrays ranges from 780nm to beyond 1 um. Coherent also have the capability to
produce the array with wide and relatively uniform spectrum for athermal pumping of solid-state lasers, by integrating
diode lasers bars with different wavelength into single array.
We describe the performance and reliability of multi-bar diode stacks assembled with hard solder attachment of the laser
diode bar to the conduction-cooled package substrate. The primary stack package design is based on a modular platform
that makes use of common piece parts to incorporate anywhere from 2-7 bars, operating at peak powers of 80W/bar to
200W/bar. In assembling monolithic type diode stack packages, it is typical to use a soft solder material such as indium
for P-side bar attachment into the package. Due to its low melting point and low yield stress, indium can provide a solder
joint that transfers low stress to the laser bar. However, during CW and QCW operation, indium is prone to migration
that can cause device failure due to a number of well-known mechanisms. This shortcoming of soft-solder bar
attachment can limit the number of shots the stack delivers over its operating life. By replacing the soft solder typically
used for P-side attachment with a hard solder, it is possible to greatly reduce or eliminate certain failure modes, thereby
increasing the operating life of the part. We demonstrate lifetime of > 1E9 shots at 80 W/bar, 250 us/40 Hz pulses, and
50C package operating temperature.
Ongoing optimization of epitaxial design within Coherent device engineering has led to a family of high power-conversion-efficiency (PCE) products on conductively cooled packages (CCP) and fiber array packages (FAP). At a 25°C heat sink temperature, the PCE was measured at 71.5% with 75W CW output power on 30% fill-factor (FF) bars with passive cooling. At heat sink temperatures as high as 60°C the PCE of these bars is still maintained above 60%. Powered by such high efficiency 9xx nm diodes, Coherent FAP products have consistently exceeded 55% PCE up to 50W power levels, with 62% PCE demonstrated out of the fiber. High linear-power-density (LPD) operation of 100μm x 7-emitter bars at LPD = 80 mW/μm was also demonstrated. Bars with 7-emitter were measured up to 140W QCW power before catastrophic optical mirror damage (COMD) occurred, which corresponds to a COMD value of 200mW/μm or 2D facet power density of 29.4 MW/cm2. Leveraging these improvements has enabled high power FAPs with >90W CW from an 800μm-diameter fiber bundle. Extensive reliability testing has already accumulated 400,000 total real-time device hours at a variety of accelerated and non-accelerated operating conditions. A random failure rate <0.5% per kilo-hours and gradual degradation rate <0.4% per kilo-hours have been observed. For a 30% FF 50W CW 9xx nm bar, this equates to >30,000 hours of median lifetime at a 90% confidence level. More optimized 30% FF 9xx nm bars are under development for power outputs up to 80W CW with extrapolated median lifetimes greater than 20,000 hours.
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.