Microheat exchanger for cooling high power laser diodes

A tremendous amount of heat is generated during operation of high power laser diodes that are built as a linear array of laser emitters. The present paper describes fabrication and test results of a microheat exchanger for cooling such high power laser diodes. The cooling module consists of two key components: a ceramic-copper bonded thermal conduction plate with twelve conducting pads to which the laser diodes are mounted and a liquid cooled microheat exchanger containing an internal active microstructure. The thermal conduction plate is joined to the microheat exchanger and the heat generated in the laser bar conduction plate is extracted by flowing a cooling liquid through the microheat exchanger. Design and fabrication of different components of the cooling module and their assembly processes are described in this paper. Thermal test results indicate that the cooling system provides uniform liquid flow and heat transfer rate over a large surface, while maintaining low pressure drop at high flow rates. Long term reliability test data demonstrate the robustness of materials, internal microstructure and fabrication processes employed in the present study.