NASA's Langley Research Center has developed a photo-acoustic sensing-based laser vibrometer for the measurement of ambient chemical species. The technology allows for detection of sub-part-per-billion (ppb) levels of ambient trace gases and chemical species, with an order of magnitude more sensitivity than similar technologies. Among other applications, the technology could be used for the detection of explosives and hazardous or toxic chemicals.
The system includes a high-repetition-rate pulsed laser module that is spectrally tuned to a desired chemical species. The photons from the laser are absorbed by the target chemical, creating an acoustic vibration that impacts a diaphragm (which acts like a speaker). A highly sensitive photo-emf detector is then used to measure the magnitude of the vibration, which corresponds to the concentration of the target chemical. The technology is being developed for NASA's trace-gas measurement needs for validation and ground truth studies to support airborne and space-based LIDAR operations. The technology has application as a chemical sniffer to detect hazardous or toxic chemical species in the vicinity of IEDs, explosives, or other chemical agents. In such an application, the sensor could detect chemical species hidden inside closed containers, bags, or car trunks.