10-W CW blue-violet diode laser array on the micro-channel cooler

Abstract

Improved light output power of blue-violet laser diodes (BVLDs) is necessary in order to use them as a light source for crystallization of amorphous silicon (a-Si) thin films to fabricate thin film transistors (TFTs). A multi-emitter BVLD array is a promising solution to obtain high light output power. For realization of the high power blue-violet laser source, we carried out a thermal design using the finite element method (FEM). Because conventional packaging is significantly affected by heat dissipation, we mounted the multi-emitter BVLD array on micro-channel coolers (MCCs). A steady thermal analysis using FEM revealed that the direct-mounted BVLD array with appropriate emitter pitch had a flatshaped transverse temperature distribution across the array. In contrast, a convex-shaped distribution was obtained when a highly thermal conductive sub-mounts, such as a diamond-composite, was inserted between the array and the MCCs. The local temperature rise in the center emitter of the direct-mounted laser array was suppressed due to their relatively shorter heat transfer paths. The flat-shaped temperature distribution should contribute to achieving high optical output power. Therefore, the BVLD arrays were directly mounted on coefficient of thermal expansion (CTE) controlled MCCs using AuSn hard solder. Under continuous wave (CW) operation, we achieved an output over 10 W with a ten-emitter BVLD array, which is the highest reported output power for a blue-violet laser source.