UHF photoparametric amplifier

Measurements on a degenerate UHF photoparametric amplifier using an optical signal modulated at 690 MHz have confirmed the 3 dB noise figure predicted by Penfield and Sawyer. The silicon photoparametric diode served as both the photodetector and varactor and was novel in several respects: the conductivity sequence was p-v-n-n⁺in contrast to the usual p-v-n⁺conventionally used for microwave photodiodes; and the diode was designed to be illuminated parallel to the p-v junction. Such a structure has an inherently high Q and features are extended optical response (quantum efficiency ≈ 10 percent at 1.06 µ), coupled with good UHF photodetection behavior, when used either as a simple (unpumped) photodiode or as a photoparametric diode.