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Biological Detector Performance with a 402 nm Laser Diode

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Technical rept.

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A previous generation of biological detection instruments, pioneered at DRES, used light sources in the 340-360 nm region. Although this wavelength region has been shown to excite important biomolecules related to live organisms, implementing them turned out to be extremely expensive due to complex technologies involved. An alternative light solution became imperative. In this paper, biological aerosol measurement was done with a laser diode emitting at 402 nm. It was chosen for its ability to excite a different class of biomolecules. There is a need to demonstrate that a fluorescence aerodynamic particle sizer FLAPS perform satisfactorily using these selected types of light sources when presented with a range of biological aerosol simulants. The findings indicated comparable fluorescence response from the select excitation sources in the presence of spore aerosol. Spores, by their physiological nature, contain very little biological material and the individual units are no larger than 0.7 m and enclosed by a very refractile spore coat. Due to this refractile characteristic, conventional light microscopy of spores reveal very little of their cellular content. In contrast, vegetative cells are better subjects for examination in that they can easily be stained. Thus, performance of biological detectors must be rated by their ability to measure spore aerosols and in these experiments, it has been shown that 10 Agent Containing Particles Per Liter of Air ACPLA could be detected. In summary, we have shown that by using a small laser diode that emits at 402 nm, it is possible to replicate the performance of 340-60 nm light sources. The findings from this study have critical implications for the future of biological detection, both for military applications as well as in environmental monitoring. With this new light source, a detector will require no active cooling system, consume little power and weigh much less than current instruments.

Subject Categories:

  • Lasers and Masers
  • Miscellaneous Detection and Detectors

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