Relation between smile effect and packaging of laser diode arrays

Smile effect is a key problem that reduces the application of laser diode arrays. This paper presents the research on the relation between smile effect and the package technology. It is found that two main parameters affect the smile effect: the uneven pressure on laser chip in soldering and the mismatch of thermal expansion coefficient. Theoretically, the uneven of the pressure can be reduced by using low thermal expansion coefficient contact bar, and the shrinkage difference between laser diode chip and heat sink can be reduced by increasing the cooling rate of the solidification process. Both theoretical and experimental results show that these methods can significantly and fundamentally reduce the smile effect.