Calculation of the homogeneous degradation of injection laser parameters from initial degradation rates

Abstract

The change of operating parameters above threshold of (Ga, Al)As injection lasers with aging time was calculated assuming a uniform mode of degradation mechanism with temperature-dependent degradation rates. In the calculation, the degradation rate for the threshold current was assumed to be temperature dependent, but not explicitly dependent on aging time and pumping current. Optical output power was kept constant during aging. The calculated time variation of laser parameters predicts a runaway after an initial slow rise. The mathematical model thus provides the means to correlate time-to-failure data with initial degradation rates and permits the evaluation of the influence of various laser parameters on lifetime. A selected group of laser diodes were aged at 80 °C under the conditions specified by the model. Degradation rates for the threshold current varied between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4 \times 10^{-5}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5 \times 10^{-4}</tex> h <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . These would extrapolate to lifetimes in excess of 10 000 h at the elevated temperature for half of the diodes in reasonable agreement with experimental values obtained by others.