Innovative, cost-effective technologies are required for Department of Defense (DoD) air emissions control applications to avoid harmful environmental impacts, major compliance-related issues, or cost escalations.
This project is developing a new class of ultra broadband (UB) radiation sources for active remote sensing of hazardous air pollutants (HAP) such as nitrogen oxides (NOx) and sulfur oxides (SOx) that are of concern to the DoD and techniques for their detection and identification through simultaneous spectral response.
The UB radiation sources provide the necessary illumination required to identify HAPs in atmospheric gases by absorption spectroscopy. UB radiation is generated by self-phase modulation of pico-second laser pulses in a nonlinear medium such as optical fiber. Because the broad bandwidth of the UB radiation can cover multiple wavelengths on the absorption bands of HAPs, more accurate and sensitive identification is possible. The methodology and diagnostics necessary to evaluate the UB spectrum are based on hyperspectral imaging techniques.
A Q-switched, mode-locked, Nd: YAG laser was used to generate UB radiation in 300 meters of fused silica optical fibers. The UB radiation spectrum extends from 1.06 to more than 2 microns. Absorption spectroscopies were performed on test HAPs and data reduction techniques were developed for analyzing the complex spectral signatures. Active remote sensing of test HAPs using UB radiation in a laboratory setting is in progress.
The UB radiation source allows multiple HAPs with absorption structures that lie within its bandwidth to be detected simultaneously. Real-time ranging and tracking at extended distances should be possible because the source size of the UB radiation is extremely small. UB radiation is especially valuable during nighttime monitoring when sunlight is not available for conventional remote sensing methods.