This study investigates the thermal performance of cryogenic micro-pin fin coolers for high-power laser diode (LD) bars. An open-loop liquid nitrogen cooling system, used to operate LD bars at cryogenic temperatures, is developed and characterized. The comparison study demonstrates that the total thermal resistance value of the micro-pin fin cooler, ranging from 0.03 to 0.04 degrees C/W, is only 1/3 of that of the micro-gap cooler and, thus, contributes significantly to reducing the LD operating temperature and enhancing its efficiency. In this study, the peak optical power of 68.8 W was observed at an LD bar package base temperature of - 100 degrees C, providing a 20% increase relative to the optical power of 57.3 W for a nominal operating condition with an LD bar package base temperature of 41 degrees C. This result clearly illustrates the enhancement in optical performance made possible by cryogenic cooling with a pin fin microcooler.
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