Down-conversion detection in 300 GHz radiation using Glow Discharge Detector (GDD)

A miniature neon indicator lamp, also known as a Glow Discharge Detector (GDD), costing about 50 cents was found to be an excellent room temperature THz radiation detector. Down conversion detection using the GDD for 300 GHz radiation is demonstrated in this study. Previous results with the GDD at 10 GHz showed 40 times better sensitivity using down conversion detection compared to direct detection. Preliminary results at 300 GHz showed better sensitivity by at least one order of magnitude using down conversion compared to direct detection. This can be improved by increasing reference beam power. In order to realize a down-conversion set up we used two synchronized THz sources based on RF multipliers. The first is a 300 GHz source and the second is a 300 GHz+Δf source, where Δf stands for the frequency difference between the two sources. Using a beam splitter configuration we combine the two frequencies for Δf=20 kHz and directed them to the GDD. Due to the unique detection mechanism of the GDD and its linear response, the difference frequency Δf was detected by the electronics circuits. We anticipate significant improvement in detection performance for higher values of Δf due to lower detector noise at higher frequencies.