Imaging with terahertz waves

We present what is to our knowledge the first imaging system based on optoelectronic terahertz time-domain spectroscopy. Terahertz time-domain waveforms are downconverted from the terahertz to the kilohertz frequency range, and the waveform for each pixel is frequency analyzed in real time with a digital signal processor to extract compositional information at that point. We demonstrate applications to package inspection and chemical content mapping in biological objects.