Catastrophic optical bulk damage in InP 7xx emitting quantum dot diode lasers

Abstract

Catastrophic optical bulk damage occurs in broad-area MOCVD-grown InP/(Al)GaInP 7xx emitting quantum dot diode lasers operated at high power with single, high-current pulses of 5–20 A, in contrast with quantum well devices, which undergo catastrophic optical mirror damage at similar power densities at the facet. After damage the quantum dot devices show a reduction in the nearfield emission intensity across the width of the facet. Panchromatic cathodoluminescence of the active region shows a decrease in intensity and reveals dark, non-radiative spots which enlarge as pulse length increases. The areal density of the spots, also present in unprocessed material from similar structures, is of the order of 106 cm−2, five orders of magnitude lower than the dot populations at 1011 cm−2. Increasing pump current pulse length to 500 ns and beyond did not increase the dark spot size, which depended on the duration of the lasing action, but decreased the cathodoluminescence intensity of both the spots and background regions inside the emitter stripe, while reference regions outside the stripe remained unchanged. These features can be used to characterize improvements in structures and growth in order to improve the performance of InP based quantum dot structures at high powers.