We present results obtained from a greatly improved version of a previously reported nitrogen dioxide monitor (Anal Chem. 2005, 77, 724-728) that utilizes cavity attenuated phase shift spectroscopy (CAPS). The sensor, which detects the optical absorption of nitrogen dioxide within a 20 nm bandpass centered at 440 nm, comprises a blue light emitting diode, an enclosed stainless steel measurement cell (26 cm length) incorporating a resonant optical cavity of near-confocal design and a vacuum photodiode detector.
View Article and Find Full Text PDFWe present details of an apparatus capable of measuring optical extinction (i.e., scattering and/or absorption) with high precision and sensitivity.
View Article and Find Full Text PDFWe present initial results obtained from an optical absorption sensor for the monitoring of ambient atmospheric nitrogen dioxide concentrations (0-200 ppb). This sensor utilizes cavity attenuated phase shift spectroscopy, a technology related to cavity ringdown spectroscopy. A modulated broadband incoherent light source (a 430-nm LED) is coupled to an optically resonant cavity formed by two high-reflectivity mirrors.
View Article and Find Full Text PDFWe discuss achievement of a long-standing technology goal: the first practical realization of a quantitative-grade, field-worthy snapshot imaging spectropolarimeter. The instrument employs Polarimetric Spectral Intensity Modulation (PSIM), a technique that enables full Stokes instantaneous "snapshot" spectropolarimetry with perfect channel registration. This is achieved with conventional single beam optics and a single focal plane array (FPA).
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