THz Applications - Linear
The second application, also passive, is called 'linear spectroscopy'...where a known THz frequency is applied to a material and the resulting spectrographic 'output' is analyzed to determine what that material is.
In essence, linear spectroscopy is the 'firing' of a 'THz bullet' at an unknown material that can eventually be identified based on the forensic analysis of the fragmented remnants of the THz bullet.
The major shortcomings of this approach are (1) the resulting THz 'fragmented remnants' are exceptionally low in energy and impossible to detect from a standoff distance; (2) the THz 'fragmented remnants' must be detected from a location opposite of the applied THz 'bullet'...tough to do when one does not know where an explosive is located to start with.
