ALGAAS VERTICAL-CAVITY SURFACE-EMITTING LASER RESPONSES TO 4.5-MEV PROTON IRRADIATION

We have irradiated single-and multimode AlGaAs vertical-cavity surface -emitting laser (VCSEL) arrays operating at a nominal wavelength of 78 0 nn with 4.5-MeV protons and doses ranging from 10 to 30 Mrad in the active region, We observed a peak power reduction of about 2% per Mrad in the 14-mu m aperture, multimode VCSEL's, Single-mode VCSEL's havin g an aperture of 6 mu m exhibited a smaller peak power reduction of 0. 4%-1% per Mrad. A slight shift in the current threshold was observed o nly for the multimode VCSEL's at dose levels above 10 Mrad, First resu lts indicate a reduced VCSEL peak laser power output that is dominated by a temperature shift caused by the radiation induced increase in re sistive heating, In contrast, the power reduction in edge-emitting las ers is dominated by the enhanced radiation induced nonradiative recomb ination rate. The VCSEL irradiation was performed with a focused ion m icro beam that was rastered over the device surface, ensuring a very u niform exposure of a single device in the array.