Program Manager: LtCol John Lowell Ph.D.

The goal of the Femtosecond Adaptive Spectroscopy Techniques for Remote Agent Detection (FASTREAD) Program is to provide a capability to detect biological agents at standoff distances. This goal will be accomplished by performing coherent nonlinear optical spectroscopy, laser pulse shaping techniques, and adaptive optics coupled to strategies that optimize the return signal from the agent under interrogation. By using short pulse lasers in conjunction with coherence effects, both the spectral and temporal information contained in the backscattered signal can be exploited, enabling identification of specific agents and providing a mechanism to adapt the system to new agents. This is in contrast to current methods that attempt to exploit either the spectral content or the temporal content but not both simultaneously. Techniques that exploit only the temporal content such as LIDAR cannot provide discrimination, while spectral measurements alone do not have sufficient specificity.

Key technical challenges include the need to—

1. Evaluate the impact of common atmospheric components, molecules of similar size, and molecules with similar physical and chemical properties on the ability to detect signals from anthrax spores. To date, in the laboratory the signals from a number of common atmospheric molecules and confusers have been collected and examined.  The data suggest that when using Coherent Antistokes Raman Spectra, the probability of detection can exceed 0.99 with low false alarm rates.
2. Develop techniques for high fidelity pulse shaping to deliver the pulse shape at the target through a dispersive and scattering atmosphere.
3. Demonstrate optimization of the backscattered S/N by adapting spectral content of the pulses, timing of the pulse sequence, and intensity of the pulses.

Remote Coherent Antistokes Raman measurements have been made of anthrax spores at a range of 200 m and efforts are under way to increase signal to noise and lower the density of molecules that can be detected

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THRUST AREA

Biological Warfare Defense

Protection and Detection