[en] In this study, broad area homostructure GaAs, single and double heterostructure GaAs/Gasub(1-x)Alsub(x)As lasers were exposed to controlled doses of ionizing radiation and the changes induced in light output, spectral and temporal characteristics were recorded. In each case, an irradiation induced increase in the threshold current (Isub(th)) and a spectral shift of the output to higher photon energies was observed. Lasers, for which the external differential quantum efficiency remained unchanged, showed a considerable irradiation induced increase in the half width Δν of the spectral output. Some lasers did, however, show a decrease in the external differential quantum efficiency and in these cases the induced increase in Δν was very much smaller. The current at which a non-linearity recorded in the light output characteristic of some lasers was attributed to the deterioration of the Fabry-Perot mode structure and it was observed that the current value involved did not change as a result of the irradiation. A non-linearity was also observed in the time delay characteristic of all the lasers studied and although the irradiation had the effect of decreasing the slopes of the two linear portions the intersection remained at approximately the same current value. The results are analyzed and discussed. (author)