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The effects of gamma total dose and gamma dose rate exposures on the operation of a state-of-the-art optical isolator were investigated. The isolator was irradiated in both 'on' and 'off' states to determine upset in dose rate environment from 1.5 x 10 to the 8th power to 2.2 x 10 to the 11th power rads(Si)/sec. High state output voltage was subject to upset at all dose rates tested. Propagation delay times, and output voltage and current were measured for total dose exposures up to 5,000,000 rads(Si). Of the parameters tested, only high state output current and low-to-high propagation delay times exceeded the manufacturer's specifications in the total dose environment. (Author)

The effect of gamma irradiation on the electrical and optical properties of amphoterically Si-doped GaAs LEDs has been investigated. The lifetime-damage constant product for degradation of the light output at constant low voltage was found to be 7.5 X 10 to the minus 7th power/rads. However, because of the presence of space charge limited current (SCLC) flow at higher currents, which conform to the practical operating range of 10 to 50 microamps, the light output degraded more rapidly than at lower voltages. It is shown that the same value of the lifetime damage constant product can be used to predict the degradation at practical operating currents when the SCLC is taken into account. Consequently, the practical implications of the results are that care must be taken in predicting degradation with a low voltage lifetime damage constant product, and that the doping conditions leading to the presence of the SCLC should be avoided for LEDs that must operate in a radiation environment. (Author), Presented at the IEEE Conference, 28 Jul 76, San Diego, Calif.

The effects of gamma radiation on optical isolators have been investigated. This study has included the simultaneous irradiation and measurement of the individual emitters and detectors making up the isolators. In this manner, the net effect of irradiation on the isolators could be attributed to the degradation of either the emitter or detector, or both. As expected, isolators containing photodiodes are more radiation resistant than those containing phototransistors. In the photodiode isolator the LED is responsible for essentially all the gamma-induced isolator degradation. The performance of phototransistor isolators depends strongly on the phototransistor bias, V sub CE, and the LED input current, I sub LED. At high I sub LED and low V sub CE where gamma-induced surface effects in the phototransistor are minimized, the degradation of the isolator is due primarily to the LED which is more sensitive than the LED in the photodiode isolator. In contrast, at low I sub LED and high V sub CE, gamma-induced surface damage in the phototransistor is the dominant effect and the isolator is quite sensitive to irradiation.