Terahertz Imaging and Sources

Imaging in the terahertz frequency range enables the detection of concealed weapons and other contraband (e.g., explosives under clothing) without the use of ionizing radiation. Spectroscopy in this frequency range has additional applications in industrial processing and remote identification of chemicals. We are using our unique capabilities in terahertz detectors, optics, metrology methods, and test-beds in these applications.

Over the past several years, we have focused on bolometric detection of THz radiation. Our initial work on cryogenic detectors has been extended to antenna-coupled bolometers operating at room temperature. These detectors provide a rugged, low-cost alternative for homeland security applications; e.g., mobile police units or portal scanners in airports. We have established that imaging in the terahertz frequency range has the potential for effectively detecting weapons and contraband concealed by clothing. We have fabricated a focal plane array of antenna-coupled bolometers and demonstrated best-in-class, real-time imaging. We will continue to explore applications of room-temperature (uncooled) and cryogenic antenna-coupled microbolometers. We perform side-by-side imaging of the same scenes with passive and actively illuminated terahertz camera systems to help settle many outstanding phenomenological questions, such as the capability of terahertz systems to selectively identify specific target materials.

We have also developed a calibrated broadband emitter for millimeter-wave through terahertz frequency regime, known as the Aqueous Blackbody Calibration (ABC) source. The ABC source is a key component of a long-range plan to establish traceability for free-space radiometric power quantities where none currently exists.

• Developed and demonstrated an ultra-wideband, sub-millimeter-wave/terahertz detector array for use in contraband detection with Valtion Teknillinen Tutkimuskeskus (VTT) of Finland.
  
• Developed and characterized the ABC source for calibrating optical power in the millimeter-wave to terahertz frequency band.
  
• Demonstrated real-time imaging of concealed contraband with a novel pasive sub-millitere-wave camera system.