Modelling threshold shift of power laser diodes under neutronic and photonic irradiation

The current threshold of high power GaAlAs laser arrays is shown to be strongly increased by fission neutron fluences, in the range 10 ¹⁴ n/cm². The current threshold after irradiation, whose value may be twice that of the unirradiated device, is associated to an anode-cathode voltage displacement. After having proved these effects are neutron specific effects, we shall propose a simplified diffusion model, which takes into account both the electrical and electro-optical threshold effects. Distributed trapped charges are assumed to modify the carrier profiles inside the active layer, Simulation configurations are described with fitting results, and we conclude that a trapped charge density in the 10¹⁴ cm^-3 range may be justified