  Here we report the results of an investigation into the effects of ionizing
radiation on commercial-off-the-shelf InGaAs and Si photodiodes. The
photodiodes were exposed to 30, 52, and 98 MeV protons with fluences ranging
from 10^8 - 5x10^11 protons/cm^2 at the Indiana University Cyclotron Facility.
We tested the photodiodes for changes to their dark current and their relative
responsivity as a function of wavelength. The Si photodiodes showed increasing
damage to their responsivity with increasing fluence; the InGaAs photodiodes
showed significantly increased dark current as the fluence increased. In
addition, we monitored the absolute responsivity of the InGaAs photodiodes over
their entire bandpass. Our measurements showed no evidence for broadband
degradation or graying of the response at the fluences tested. All measurements
in this investigation were made relative to detectors traceable to NIST
standards.
