Noise performance of microwave-biased photoconductive detectors

Abstract

A description of the noise performance of microwave-biased photoconductive detectors is proposed. The theoretical results are confirmed by experimental results on an uncooled detector using germanium as the photoconductor. In this case generation-recombination noise caused by thermally generated carriers dominates at low frequencies (<10MHz). At higher frequencies only the noise of the microwave-receiver has to be considered. It is shown that the ultimate limit of the sensitivity of a microwave-biased photoconductor and a d.c.-biased photoconductor are equal but because of its higher internal gain it is easier to obtain this limit with a microwave-biased detector. The noise-equivalent-power of 6.10 −14 W/√Hz ( f s = 1 MHz) measured at room temperature at a wavelength of 1.5 μm is considerably superior to the best values of uncooled conventional detectors.