Carbon-Composite Heat-Sinking Submounts for Laser Diodes

Carbon-composite submounts tipped with diamond are being developed as improved means of dissipating heat generated in high-power laser diodes. Copper is the traditional heat-sinking material for many applications other than laser diodes; it is not suitable for heat-sinking submounts for laser diodes because its coefficient of thermal expansion (CTE) is too high to enable an acceptably close match to the CTEs of laser-diode semiconductor materials. Heretofore, heat-sinking submounts for laser diodes have been made from a copper/tungsten alloy, chosen because of its rigidity and its low CTE, which matches the CTEs of the laser-diode semiconductor materials more closely than copper does. Unfortunately, the thermal conductivity of the copper/tungsten alloy is only 45 percent of that of copper. In contrast, the carbon composites of the present development can be made to have both low CTEs and effective thermal conductivities of the order of three times that of copper.