Catastrophic optical bulk damage (COBD) processes in aged and proton-irradiated high power InGaAs-AlGaAs strained quantum well lasers

摘要

Recent remarkable success of fiber lasers and amplifiers results from continued improvements in performance characteristics of broad-area InGaAs-AlGaAs strained quantum well (QW) lasers. Unprecedented characteristics of single emitters include optical output powers of over 20 W and power conversion efficiencies of over 70% under CW operation. Leading high power laser diode manufacturers have recently demonstrated encouraging reliability in these lasers mainly targeted for industrial applications, but long-term reliability of these lasers has never been demonstrated for satellite communication systems in the space environment. Furthermore, as reported by two groups in 2009, the dominant failure mode of these lasers is catastrophic optical bulk damage (COBD), which is a new failure type that requires physics of failure investigation to understand its root causes. For the present study, we investigated reliability, proton radiation effects, and the root causes of COBD processes in MOCVD-grown broad-area InGaAs-AlGaAs strained QW lasers using various failure mode analysis (FMA) techniques. Two different approaches, accelerated life-testing and proton irradiation, were taken to generate lasers at different stages of degradation. Our objectives were to (i) study the effects of point defects introduced during crystal growth and those induced by proton irradiation with different energies and fluences in the lasers on degradation processes and to (ii) compare trap characteristics and carrier dynamics in pre- and post-stressed lasers with those in pre- and post-proton irradiated lasers. During entire accelerated life-tests, time resolved electroluminescence (TREL) techniques were employed to observe formation of a hot spot and subsequent formation and progression of dark spots and dark lines through windowed n-contacts.