A four-pad 3 method was developed for determining the thermal conductivity of bulk and thin film materials. The heat conduction in the sample geometry was investigated by numerical simulation employing the finite volume technique. As a result, the conditions ͑i.e., sample geometry, frequency range͒ can be predicted when conventional analytical formulas are suited to determine the thermal conductivity of bulk and thin film material from the data measured. Experiments were performed that confirm the validity and accuracy of the numerical calculations.

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The transient thermal properties of high-power diode laser bars with active and passive cooling are analyzed. Both thermal imaging and the analysis of the thermal wavelength tuning behavior are employed to extract the device temperature as a function of time. A steady-state thermal situation is established with rise times of about 10 and 60ms for active and passive cooling, respectively. The latter number, however, is substantially increased by the particular properties of the external heat sink. Such results are confirmed by model calculations based on the finite element method.

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