Comparison of atmospheric transmission in the bands ranging from terahertz (THz) to infrared (IR) bands using MODTRAN and available literature data show that THz radiation is not dramatically attenuated in adverse conditions when compared to IR bands especially at long distances. Favorable THz bands and mechanisms for detection of low IR signature target under adverse conditions in these bands are determined. In this study, a set of experiments are conducted to compare THz detection mechanisms, which are THz detectors and IR microbolometer cameras. Typically, IR Microbolometer cameras are not sensitive enough to detect THz waves and their sensitivity needs to be improved. While THz microbolometer cameras are being continuously improved the use of a THz to IR converter intermediary component allows a cost-effective solution to the problem. A THz to IR converter based on a metasurface absorber is studied in this regard. The effectiveness of the device is simulated and the temperature difference that can be detected with the IR microbolometer camera is modeled based on heat transfer equations.
Millimeter (mm) and sub-mm wave radiation is increasingly becoming a region of interest as better methods are developed to detect in this wavelength range. The development of sensitive focal plane array (FPA) architectures as well as single pixel scanners has opened up a new field of passive detection and imaging. Spectral signatures of objects, a long standing area of interest in the Short Wave Infrared (SWIR), Mid-Wave (MWIR) and Long Wave-IR (LWIR) bands can now be assessed in the mm-wave/terahertz (THz) region. The advantage is that this form of radiation is not as adversely affected by poor atmospheric conditions compared to other bands. In this study, a preliminary experiment in a laboratory environment is performed to assess the radiance from targets with low infrared signatures in the millimeter wave/terahertz (THz) band (<1 THz). The goal of this approach is to be able to model the experimental results to better understand the mm-wave/THz signature of targets with low observability in the IR bands.