Integration of a Mobile Terahertz Spectroscopic System based on HEB Heterodyne Detection

Abstract—We are developing a mobile heterodyne terahertz system based on hot electron bolometer (HEB) mixer receivers to both image and obtain spectra from biological samples. An HEB mixer provides unprecedented sensitivity and spectral resolution at terahertz frequencies. We have recently demonstrated a low-noise heterodyne passive imager operating at 0.85 THz [1]. A heterodyned HEB detector integrated with a low noise amplifier and quasi-optical beam handling based on polymer lenses are central to this radiometric system. The current design is optimized for the atmospheric windows centered at 650 GHz and 850 GHz, but can be extended to any terahertz frequency. A state-of-the-art mechanical cooler with a very small footprint, high temperature stability, and low mechanical vibrations is also under development for our HEB receiver technology. Here we report the integration of these different elements into one platform that will result in a flexible, mobile, and versatile diagnostic instrument capable of long-term, low-maintenance operation in biomedical applications. We intend to perform real-time tissue diagnosis using broadband terahertz spectroscopy that is guided by terahertz imaging with a spot size of 500 micrometers or less with this mobile platform. Index Terms—Heterodyne detection, hot electron bolometer (HEB) detectors, quasi-optical coupling, radiometry, terahertz imaging, terahertz spectroscopy. I