High-power near-Infrared LED (IRED) are gaining more and more interest in a large variety of commercial, industrial
and military applications.
IRED are based on InAlGaAs semiconductor structures which cover a spectral range of 780 nm to 1100 nm. This
wavelength range is supposed to be not visible to the human eye. But, depending on the radiant intensity and wavelength,
a reddish glow is still evident. Therefore, in covert applications longer wavelength of 940 nm or even higher are
preferred due to the much lower sensitivity of the human eye compared to 850 nm. On the other hand at around 850 nm
the spectral sensitivity of CMOS or CCD cameras or other silicon based photo detectors is at its maximum. We present
the latest developments in high power IRED in the quest for more than 1 W from a single 1mm2 die.
Laser dies in an optical power range of 1-3 Watts are widely assembled in popular TO- packages. TO-packages suffer
from high thermal resistance and limited output power. Bad thermal contact between circuit boards and TO-devices can
cause overheating of laser chips, significantly reducing the operating life time. We developed a compact high heat-load
SMT package for an optical power up to 7 Watts in CW operation with good life time results.
The new package for high power laser chips combines highly efficient heat dissipation with Surface-mount technology.
A Direct-Bonded-Copper (DBC) substrate acts as a base plate for the laser chip and heat sink. The attached frame is used
for electrical contacting and acts as beam reflector where the laser light is reflected at a 45° mirror. In the application the
DBC base plate of the SMT-Laser is directly soldered to a Metal-Core-PCB by reflow soldering. The overall thermal
resistance from laser chip to the bottom of a MC-PCB was measured as low as 2.5 K/W. The device placement process
can be operated by modern high-speed mounting equipment. The direct link between device and MC-PCB allows CW
laser operation up to 6-7 watts at wavelengths of 808nm to 940nm without facing any overheating symptom like thermal
roll over. The device is suitable for CW and QCW operation. In pulsed operation short rise and fall times of <2ns have
been demonstrated.
New application fields like infrared illumination for sensing purposes in the automotive industry and 3D imaging
systems could be opened by this new technology.
Adaptive Cruise Controls (ACC) and pre-crash sensors require an intelligent eye which can recognize traffic situations and deliver a 3-dimensional view. Both microwave RADAR and “Light RADAR” (LIDAR) systems are well suited as sensors. In order to utilize the advantages of LIDARs -- such as lower cost, simpler assembly and high reliability -- the key component, the laser diode, is of primary importance. Here, we present laser diodes which meet the requirements of the automotive industry.
We have investigated high-power diode laser bars from 808 nm to 980 nm. The presentation is focussed upon the development of suitable laser bars for improved beam quality at increased output power. For better beam shaping structures with reduced fill factor of 30% were developed. They were operated in continuous wave mode at power levels of up to 60W. Moreover industrial applications require lifetimes of more than 10,000 hours. We present data yielding an extrapolated lifetime of up to 100,000 hours at 40W with 60% wall-plug efficiency at 980nm cw.
Martin Behringer, Marc Philippens, W. Teich, Alexis Schmitt, Stefan Morgott, Joerg Heerlein, Gerhard Herrmann, Johann Luft, G. Seibold, Jens Biesenbach, Thomas Brand, Marcel Marchiano
KEYWORDS: Semiconductor lasers, Diodes, Polarization, Multiplexing, High power diode lasers, Collimation, High power lasers, Laser cutting, Laser development, Printing
The introduction of high power diode laser systems in industry has boosted the interest in these devices for a wide range of applications. Besides printing and soldering, cutting and deep penetration welding are becoming more important. An overview about the developments, an update on today's high power laser activities and an outlook will be given, what characteristics laser bars will have to fulfil in the near future.
For higher brightness, laser bars with lower fill factors, monolithic integrated laser junctions and tapered laser designs were investigated. High power diode laser (HPDL) bars with 25% - 50% fill factor were operated between 40 W and 80 W and lifetimes up to 100 000 hours could be extrapolated. Tapered laser bars with 50W output power and high wall plug efficiencies were developed.
Wavelength multiplexing and polarisation coupling were used in order to reach multi-kilo-Watt diode laser emission. Examples for applications will be given.
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