Terahertz imaging and spectroscopy based on hot electron bolometer (HEB) heterodyne detection*

Imaging and spec troscopy at terahertz fre quencies have great po tential for healthcare, plasma di ag nos tics, and homeland secu rity ap pli ca tions. Terahertz fre quen cies cor re spond to en ergy level tran si tions of im por tant mol e cules in bi ol ogy and as trophys ics. Terahertz ra di a tion (T-rays) can pen e trate cloth ing and, to some ex tent, can also pen e trate bi o log i cal ma te ri als. Because of their shorter wave lengths, they of fer higher spatial resolution than do microwaves or millimeter waves. We are developing hot electron bolometer (HEB) mixer receivers for heterodyne detection at terahertz frequencies. HEB detectors provide unprecedented sensitivity and spectral resolution at terahertz frequencies. We describe the development of a two-pixel focal plane array (FPA) based on HEB technology. Furthermore, we have demonstrated a fully automated, two-dimensional scanning, pas sive imaging system based on our HEB technology operating at 0.85 THz. Our high spectral resolution terahertz imager has a to tal sys tem noise equivalent temperature difference (NE T) value of better than 0.5 K and a spatial resolution of a few millimeters. HEB technology is becoming the basis for advanced terahertz imaging and spectroscopic technologies for the study of biological and chemical agents over the entire terahertz spectrum.