Real time THz imaging based on frequency upconversion

We demonstrate video rate-terahertz imaging based on upconversion of THz pulses to the infrared. Mixing of narrow bandwidth THz pulses (centered at 1.5 THz) with strong IR pulses at 1064 nm generates sidebands separated from the IR spectrum by the THz frequency. Removal of the strong IR background enables high speed detection of the upconverted signal with a CMOS camera. Real time imaging of concealed objects is demonstrated with this system.