This Small Business Innovation Research (SBIR) Phase I project is focused on the demonstration of a real-time high-contrast Terahertz (THz) imaging system, based on frequency upconversion of THz images into the near infrared (NIR) spectral range. Due to low power of compact THz sources and poor sensitivity of room-temperature THz detection techniques, imaging systems operating in 0.3-3 THz range of frequencies remain far less advanced than optical or microwave instruments. Upconversion of THz radiation to NIR enables the use of imaging systems based on faster, more sensitive NIR detectors and detector arrays. This technique has been demonstrated in the past, using broadband THz combined with femtosecond NIR pulses, but the contrast of these real-time THz images was limited. The objective of this project is to demonstrate high contrast, real-time THz images using upconversion of high power narrowband THz and picosecond NIR pulses in quasi-phase matched crystals. This approach will provide upconverted THz-NIR images that can be spectrally filtered from the background NIR light, significantly improving the contrast. The high contrast between signal and background should allow for real time THz imaging using readily available NIR cameras and recently developed high power narrowband THz sources.
The broader impact/commercial potential of this project ranges from terahertz (THz) imaging systems for cancer screening to airport security systems. Millimeter wave imaging systems, operating at 20-30 GHz frequencies, are being deployed in airports now. THz cancer screening instruments have been in trials for a few years and have shown great promise in the early detection of certain types of cancers. There are a variety of industrial and security applications for non-destructive evaluation using THz waves, which are not heavily absorbed or scattered by fabrics, plastics and many composite materials. These and many other potential applications of THz have been tested by researchers around the world for decades, but very few THz instruments reached the broader scientific community and none are widely used in the industry today. Limited sensitivity, long processing time of THz imaging systems, and limited spectral bands not absorbed by water are the main barriers for wider applications of these instruments. The proposed project targets all of these barriers, focusing on a water transmission window at 1.5 THz and potentially enabling much more practical THz instruments for a broader research and industrial community.
