Adding a heat bypass improves the thermal characteristics of a 50 μm spaced 8-beam laser diode array

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Abstract
Because heat transferred between closely spaced elements in a compact laser diode array shortens array lifetime and affects the elements’ operating characteristics, we evaluated the effect of a heat‐bypass structure by measuring the thermal resistance of array elements. We estimated thermal resistance by measuring differences between junction voltage before and after injecting subthreshold current pulses. The thermal resistances due to self heating were more than 20% lower after adding the heat‐bypass structure. This effect was greatest for elements whose thermal resistance was initially highest, and it was proportional to the number of operating elements. The bypass structure therefore also reduced the thermal resistance resulting from simultaneous operation of all eight elements by more than 40%. The resultant reduction in the junction temperature of array elements operating at 100 mW would increase array lifetime at least threefold.