|
When laser diodes exceed 1000 nm wavelengths, their efficiencies drop significantly. For example, at
optical outputs of 50 - 100 W, they need to dissipate 250 - 500 W of heat. In addition, their temperature
drifts must be minimized, particularly when multiple laser bars are coupled together.
While laser diodes can be water cooled, this approach is often not acceptable. As an alternative,
Munich-based AMS Technologies AG was tasked to design and build thermoelectric plate-to-air cooling
units.
Heat from each 1 x 10 mm laser bar was spread out by a 25 x 25 mm submount, and one or more submounts,
in turn, were attached to a larger base plate in accordance with optical and electronic design
considerations. The resulting heat transfer was very complex involving an interplay between heat
generation and spreading, Peltier effect within the TEC array and the air flow removing heat from the TEC
heat sink. This called for CFD analysis using software with proven TEC models.
AMS picked Coolit, used by top TEC manufactures because of its most sophisticated model of TECs in the
market. The model incorporate G-factor, the number of couples, Seebeck coefficient (either constant or as
a function of temperature), etc. The analysis predicted that if each laser bar were mounted on an 8 mm
thick copper plate, it could be adequately cooled by a 40x40 thermoelectric array. The prototype testing
confirmed Coolit predictions to within 5%.
|
