Thermal interaction in a distributed-feedback laser diode (DFB LD) array module

The thermal interaction in a four-element distributed-feedback laser diode (LD) array module is investigated. When the injection current of each element was 200 mA, the interactive temperature rise of an element at one end was 6.6 degrees C. At the same time, temperature rise of the mounting structure (submount, header, and heatsink) was 4.9 degrees C, or about 75% of the interactive temperature rise of the element. According to two-dimensional thermal analysis, the temperature rise of the mounting structure accounts for 98% of the interactive temperature rise of the element. These experimental and analytical results show that the temperature rise in the mounting structure is the main cause of the interactive temperature rise of this module. Stabilization of the submount temperature instead of the heatsink temperature reduced the interactive temperature rise due to the three neighboring elements to 1/3 of that achieved by conventional heatsink temperature stabilization. The thermal analysis also showed that a thicker submount further reduces the thermal interaction in an LD array module.