Thermal impedance of diode lasers: Comparison of experimental methods and a theoretical model

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Abstract
The thermal impedances of double heterostructure, oxide isolated, stripe geometry diode lasers were measured and compared to a calculated value from a theoretical heat-flow analysis. The lasers had a stripe width of 8 μm and a cavity length of 250 μm, and were bonded with indium solder to a gold/nickel plated copper block. The measurement techniques were based upon the variation with active region temperature of four different device parameters: the terminal voltage, the emitted optical power, the longitudinal-mode spectrum, and the lasing threshold current. As predicted by the theoretical analysis, the thermal impedance measurements based upon the various parameters yielded the same measured thermal impedance, indicating that each parameter responded to the same average active region temperature. The range of values measured for different diodes was 33 to 79 °C/W, compared to the theoretically calculated value of 25 to 30 °C/W. The wide range of measured values is attributed to irregular conditions associated with the indium bond.