Advanced Development for Defense Science and Technology

This SBIR project is designed to develop a high-sensitivity optical spectroscopic method for rapid health screening and monitoring including warfighter field diagnostics and, potentially, detection of chemical warfare agents. The method called noise-immune, cavity-enhanced, optical heterodyne spectroscopy (NICE-OHMS) was invented about 10 years ago, but has been considered too complex for commercial development. We are taking advantage of recent improvements in enabling technologies to make NICE-OHMS reliable, rugged, and portable. We anticipate, by the end of Phase II, two-to-four orders of magnitude sensitivity improvement over competing spectroscopic methods with only a modest increase in cost. All previous NICE-OHMS research has used gas samples at reduced pressure because the laser modulation conditions are dictated by the widths of the spectroscopic lines being probed. These widths increase with increasing pressure. One key part of our work is shifting operation to atmospheric pressure samples. This has the obvious advantage of simplifying NICE-OHMS by eliminating vacuum pumps and control valves; on the other hand it requires modulation frequencies exceeding 1 GHz. Suitable inexpensive components have only recently become commercially available. These were tested successfully in Phase I and are key parts of the Phase II prototype spectrometer.