Sensors

The Chemical, Microsystem, and Nanoscale Technologies Group also develops sensors to detect trace chemicals in the environment. The group has developed both point and standoff sensors for the detection of trace aerosols, vapors, and trace chemicals on surfaces.

PDLIF fingerprint detectionThis image shows the ability of PDLIF to image the particles of TNT comprising a contaminated fingerprint.

The group has developed bioaerosol point sensors that use a combination of elastic scattering, laser-induced fluorescence, and elemental analysis to distinguish potentially harmful bioaerosols from the aerosol background. Similarly, the group is developing aerosol sensors to perform chemical identification by using differential infrared elastic scattering and Raman spectroscopy. Another effort is investigating the sensing of trace chemicals on surfaces by using active, multi- and hyperspectral, long-wave infrared imaging. This effort leverages emerging laser technology, such as multiwavelength quantum cascade laser arrays developed in collaboration with the Laser Technology and Applications Group.


In the area of explosives sensing, photodissociation followed by laser-induced fluorescence (PDLIF) was demonstrated and field tested for the remote detection of explosive trace materials. In addition, the group has codeveloped with the Active Optical Systems Group within the ISR and Tactical Systems Division a technique called Photoacoustic Sensing of Explosives (PHASE), which detects trace levels of explosive residue on surfaces. This technique exploits acoustic emissions resulting from the absorption of short ultraviolet pulses by explosive traces on surfaces. These emissions can be measured and detected remotely using a laser vibrometer, which is a key discovery that enables detection of chemical traces from standoff distances. In 2013, PHASE was awarded an R&D 100 Award from R&D Magazine.

The group has also developed another form of acoustic spectroscopy, called Dynamic Photoacoustic Spectroscopy (DPAS), which remotely generates an acoustic shock wave by scanning an infrared laser beam at Mach 1 through the plume being interrogated. When combined with rapidly tunable infrared lasers, DPAS allows for discriminant detection of chemical vapors from standoff distances.

In addition to these laser-based methods, the Chemical, Microsystem, and Nanoscale Technologies Group has programs developing reagents and optoelectronic instruments for colorimetric, fluorescent, and chemiluminescence-based detection.

 

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