Thermal and package design of high power laser diodes

Thermal and package design is carried out for high power laser diodes. Both junction-up and flip-chip configurations are studied. The flip-chip technique is far superior to the junction-up method. For a 300-μm(L)×500-μm(W) GaAs laser diode chip with active region of 300 μm(L)×5 μm(W), the flip-chip design gives a thermal resistance of 30.14°C/W using a diamond heat sink, and 41.72°C/W using a copper-tungsten heat sink. Calculated result shows that the temperature along the active region is uniform for uniform heat flux. It is thus recommended that the laser chip be designed with uniform heat flux rather than uniform current density along the active region. A technology is suggested to perform flip-chip bonding of the laser chip without incurring the danger of solder getting onto the laser facets