Effect of electrical and thermal stress on low-frequency noise characteristics of laser diodes

In this paper, we study the electrical noise of commercially available laser diodes: a group of index guided AlGaInP diodes lasing at 635 nm (SDL3038-11) and a group of InGaAlP-multi-quantum-well diodes lasing at 670 nm (SVL71B). In particular, the effect of stress (high current and high temperature) on the noise is investigated. Measurements of the magnitude of the 1/f noise as a function of the operating current (10 nA to 10 mA) revealed an anomaly. After increasing proportionally with the current at small currents (10 nA to 10 muA), the 1/f noise tends to saturate with increasing currents in the range from 10 to 100 muA. For larger operating currents, the 1/f noise increases again with the current, proportional to I-2. This anomaly is even more pronounced after the devices have been stressed. We conclude that measurements of the 1/f noise at low bias currents are sensitive to the degradation of the active region of the laser diodes, while measurements of the 1/f noise at high bias currents can predict, failure related to the quality of the crystal layers of the laser diodes. (C) 2001 Elsevier Science Ltd. All rights reserved.