Double conversion heterodyne photoparametric amplifier

The Photoparametric Amplifier, or PPA, is a useful concept in the possible approaches to low noise optical detection, combining optoelectronic conversion with gain in a potentially very low noise manner. The process is conventionally associated with frequency changing as well, and operates in the frequency upconversion mode, leading to a gain which is dependent on the ratio of pump frequency to signal modulation frequency. In the work reported here, we demonstrate a dual approach in which there is a second stage mixer, which restores the original signal spectrum to baseband at the output, with an overall conversion gain of around 10 dB using passive mixing, and typically 21 dB if an active mixer is used.