Thermal resistance and optimal fill factor of a high power diode laser bar

Using analytical methods, we obtain compact theoretical expressions for the electrical and thermal resistances of a laser bar as a function of its fill factor. The theoretically determined values of the thermal resistance are in excellent agreement with the measured ones. We use the theoretical values of the electrical and thermal resistances to find the fill factor that gives the maximal output power for a given active region temperature and the fill factor that gives the minimal active region temperature for a given output power. The optimal fill factor is dependent on the bar operating regime; higher power operation favours the use of higher fill factors to minimize the active region temperature rise.