A RadOptic detector, which was optimized to respond to MeV pulses utilizing bulk semiconductors and an interferometer method, was reported. The interferometer in the detector consisted of a C-band, continuous-wave, narrow-bandwidth laser, single-mode fibers and a bulk semiconductor. The instantaneous refractive index change induced by a MeV pulse was recorded in one shot by an optic-electrical detector. The relationship between the gamma pulse and the detector output pattern was theoretically deduced and experimentally tested with incident MeV pulses. The pulsed gamma source had a 0.8 MeV (max) energy and 60 ns duration. The detector with an intrinsic GaAs sample, whose recombination time was approximately 0.6 ns, as measured by double photon absorption, was an impulsive detector, demonstrating a pattern the output represents the gamma-pulse strength. The detector with an intrinsic InP sample (a recombination time of approximately 1000 ns) was an integral detector, and the differential of the output pattern was consistent with the gamma pulse. A long-distance (~ 1 km) and high temporal resolution (better than 2 ns) detector for MeV pulses was created in this work.
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