Radiometric Millimeter-wave detection via optical upconversion and carrier suppression

We report a novel technique for radiometric detection of radiation in the millimeter-wave regime based on optical modulation. Millimeter-wave energy modulated onto an optical carrier is detected using a low-bandwidth photodetector with optical filtering to suppress the carrier. Using this technique, we have achieved noise-equivalent powers as low as 20 pW/spl radic/Hz for a 44-GHz narrow-band signal using chopping techniques. Such detection was implemented using commercially available components and without RF or optical amplification. Further improvements in sensitivity are expected as the setup is optimized for operation in the frequency band of interest.