tEchnology cooling
Running cool T
The lifetime of laser diode bars is limited by the way they are cooled. nadya Anscombe looks at different possible solutions to the problem
here is no question that laser diodes are increasing in power every year. While this increase in power brings new applications and new markets, it
also brings with it a big problem – waste heat. The main challenge facing laser diode
manufacturers today is not how to make more powerful lasers, but how to cool them so that they last long enough to be of use. The lifetime of the package, which houses the laser diode bar and the cooling mechanism, is today the limiting factor in many laser diode applications. The most common method of removing large amounts of waste heat in laser diode arrays is through the use of copper-based microchannel coolers. These involve pumping a cooling liquid through the microchannels to remove the heat. In the majority of commercially-available coolers, the coolant is in electrical contact with the diode bars. This requires the use of deionised water, which places increased demands on the cooling
22 ElEctro optics l OCTOBER 2011
system and also causes erosion and corrosion, and ultimately, failure of the microchannel coolers.
Michael Leers is head of the packaging
group at Germany’s Fraunhofer Institute for Laser Technology. He says: ‘New cooling technologies are urgently needed, but so far no technology has replaced copper microchannel coolers. Companies seem to accept the fact that after 10,000 to 25,000 hours they will need to change their laser arrays despite the fact that it is usually the cooling technology and not the laser that needs replacing. Any technology aimed at replacing conventional cooling systems will have to demonstrate a lifetime of more than 20,000 hours and this is why we have not seen any new viable technology for several years.’ However, he believes there are several
developments in the pipeline that show great promise. Companies around the world are working with new materials such as copper
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