An explosives detection instrument was designed and tested at SRI Inte
rnational. The instrument uses frequency modulation spectroscopy with
midinfrared lead-salt diode lasers to perform high-sensitivity detecti
on of characteristic nitrogen-containing decomposition products of exp
losives. Ultimately, the instrument should be capable of detecting and
identifying subpicogram levels of plastic explosives, which would be
suitable for screening passengers at airports. Using the laboratory br
eadboard instrument and two different explosive vapor generators, we d
emonstrated a lower limit of detection of 5-10 pg for cyclotrimethylen
e trinitramine and linearity of the signal over an order of magnitude.
(C) 1996 Optical Society of America