We report on the delivery of low energy ultra-short (<1 ps) laser pulses for laser induced breakdown
spectroscopy (LIBS). Ultra-short pulses have the advantage of high peak irradiance even at very low pulse
energies. This opens the possibility to use compact, rare-earth doped fiber lasers in a portable platform for
point detection applications using LIBS for elemental analysis. The use of low energy ultra-short pulses
minimizes the generation of a broad continuum background in the emission spectrum, which permits the use of
non-gated detection schemes using very simple and compact spectrometers rather than large and delicate
intensified charge-coupled devices (ICCDs). The pulse energies used to produce high-quality LIBS spectra in
this investigation are some of the lowest reported and we investigate the threshold pulse requirements for a
number of near IR pulse wavelengths (785-1500 nm) and observe that the pulse wavelength has no effects on
the threshold for observation of plasma emission or the quality of the emission spectra obtained.
Intense laser pulses may be used for standoff detection of energetic materials. Coherent backscattered
spectroscopy offers a tremendous advantage over other spectroscopic detection techniques in that it uses stimulated or
amplified spontaneous emission from the sample to produce a minimally divergent, directional beam back to the
detection platform. The characteristics of the backscattered beam depend largely on the intensity and pulse width of the
laser source as well as the concentration and photo-physical characteristics of the target molecule. Different target
molecules will exhibit different backscattered emission signals, allowing differential detection of energetic materials in
the vapor phase. Because of the highly directional nature of the coherent backscattered beam, detection limits in the
vapor of less than 1 ppm at ranges up to 100 meters can be anticipated.
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