Transient thermal behavior of high power diode laser arrays

Reliability and lifetime of high power laser arrays are governed by their thermal properties. Thus the understanding of the thermal behavior such as thermal transients as well as the optimization of laser chips and mounting are key features for obtaining improved devices. We present numerical simulations of the active layer temperature employing the finite element method (FEM). Both continuous wave (cw) operation and thermal transients are modeled within a unified theoretical concept, which basically connects a balanced equation model that provides information on the temperature dependence of the loss mechanisms, such as spontaneous emission, Auger and surface recombination with a 2 dimensional FEM model. For a given laser array architecture we calculated the effect of the introduction of different heat spreader materials such as copper, silicon and diamond, Furthermore, different array designs such as broad area devices and stripe arrays having different output power (cw: 1-10 W) are numerically described. These results are compared with experimental data on the averaged temperature of the optically active layer. The temperature values are determined from the spectral shift of the emission spectrum of the array at a certain time windows after applying the operation current. Both experimental and theoretical results are compared from the 10 ns to the cw range. Thus both the theoretical description concept as well as the parameter set used for the calculation are carefully tested. Remarkable agreement between calculated and measured thermal transients was found. Additionally, the very divergent temporal behavior of special array structures was verified coincidentally by theory and experiment.