Degradation of heterojunction laser diodes under electron beam irradiation

摘要

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 90 Mrad was achieved at room temperature, and the irradiation geometry was an axial one. The measurements were performed off-line. An automatic measuring set-up was developed including various instruments: a laser diode driver, a laser power meter, a wavelength meter, a fiber optic spectrometer and a laser beam analyzer. After each irradiation step, the following characteristics were monitored, as function of the driving current and laser 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 (extended graphical information is provided in the paper). The following changes were noticed: an increase by 6 % for the threshold current, a drop by 7 % for the quantum efficiency, a decrease by 9 % for the photodiode responsivity, and a slight modification of the wavelength of the emitted radiation.