Degradation of heterojunction laser diodes under electron beam irradiation

We are reporting the investigation on the degradation of heterojunction laser diodes as they were subjected to electron beam irradiation. The research was done under the European Union's Fusion Programme, and targets the possible use of semiconductor lasers for remote sensing and robotics, under irradiation conditions. A total irradiation dose of 600 kGy was achieved at room temperature. The measurements were performed off-line using an automatic measuring set-up. Following each irradiation step, several characteristics of the laser diodes were monitored, as function of the driving current and the case temperature: the emitted optical power, the wavelength of the emitted radiation, the embedded photodiode current, the longitudinal and transversal mode structure, as well as the temporal behavior of all these parameters. For each irradiation dose, the laser diode serial resistance, threshold current, and quantum efficiency, and the photodiode responsivity were plotted for different operating conditions.