Proton damage in advanced laser diodes

Proton radiation damage in laser diodes is investigated for several types of laser diodes with wavelengths from 650 to 1550 nm. Key parameters include slope efficiency, threshold current, and the transition characteristics between laser-emitting diode (LED) and laser operation. Some of the devices exhibited nonlinear relationships between threshold current and proton fluence. All of the lasers, including vertical-cavity surface-emitting lasers, were strongly affected by recombination-enhanced annealing, in contrast to double-heterojunction LEDs, which are only slightly affected by annealing. Analysis of laser characteristics after irradiation showed that the main effect of radiation damage is an increase in bulk recombination that increases loss within the laser cavity.