Thermal analysis of high power laser diodes by electro-thermal indirect coupling finite-element method

Since the invention of laser diodes, research on thermal management has become a hot topic during last decade because the problem not only restrict output power of the laser diodes but also influence the reliability of the devices. Electro-Thermal indirectly coupling method was used to calculate temperature distribution of a CW p-side-down high power diode laser, the result show that the highest temperature of p-side-down laser diode is just 34.7°C, which is lower than that of 51.1´C calculated by simply thermal method. Experiment result indicated that the junction temperature is 36.7°C which is more closer to the indirectly coupling method. Temperature of p-side-up diode laser is also studied by FEM and the result shows that the temperature is as high as 90.9 °C, therefore the p-side-down method is priority than p-side-up method. Relationship between emitter width/cavity length and junction temperature has also been investigated, the result shows that with the increasing of emitter width and cavity length the junction temperature reduce rapidly. Thermal effect of the diode laser working at QCW mode has also been studied. When the repetition rate is 1kHz and pulse width is 200μs, the temperature at end of period is equal to ambient temperature even the peak current reach to 1000A. The temperature at end of period is also equal to ambient temperature when the pulse width is at 600μs. But when the repetition rate increase to 6kHz, the temperature at end of period would be increased rapidly with the peak current is 255A.