Effects of gamma radiation on high-power infrared and visible laser diodes

The effects of gamma radiation on high-power semiconductor laser diodes were measured. While operating, five commercial near-infrared (785 nm, 60 mW) and six visible laser diodes (670 nm, 30 mW) were exposed to approximately 10 kGy at a relatively high dose rate (≈5 kGy/h). The far-field, output beam patterns were monitored during radiation and recovery, as well as the overall intensity (constant current mode) and the internal monitor photodiode current. The linear dimensions of the far-field beam patterns shrank in size by the end of radiation by 3%-20% for the IR lasers and 15%-20% for the visible. The ellipticity of the beams changed by -16% for the IR and +8% for the visible case. The intensity, as measured with an external camera, decreased during irradiation by a maximum of 2.7 dB for the visible laser and 2.5 dB for the infrared; however, the photodiode photocurrents changed by less than 1 dB. Both types of lasers recovered completely over several days. The near- and far-field patterns were examined both below and above threshold before and after radiation/recovery, with no evidence of defects or other gross changes