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We have irradiated single- and multimode AlGaAs vertical-cavity surface-emitting laser (VCSEL) arrays operating at a nominal wavelength of 780 nm 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-μm aperture, multimode VCSELs. Single-mode VCSELs having an aperture of 6 μm exhibited a smaller peak power reduction of 0.4%-1% per Mrad. A slight shift in the current threshold was observed only for the multimode VCSELs at dose levels above 10 Mrad. First results indicate a reduced VCSEL peak laser power output that is dominated by a temperature shift caused by the radiation induced increase in resistive heating. In contrast, the power reduction in edge-emitting lasers is dominated by the enhanced radiation induced nonradiative recombination rate. The VCSEL irradiation was performed with a focused ion micro beam that was rastered over the device surface, ensuring a very uniform exposure of a single device in the array.