Remote Fiber Optic Sensor for Gaseous and Liquid Environments. Phase 2

摘要

The goal of this program was to develop techniques and instrumentation for theimplementation of Raman spectroscopy as a chemical sensor for both gas and liquid phase samples. Surface enhanced Raman techniques have been employed for low level detection. Novel SERS substrates have been demonstrated which enable complexation and preconcentration of gas phase species, a new development since SERS had previously been associated only with the liquid phase. 'ne substrates were demonstrated for Raman sensing of hydrazine, ethanol, dimethyl methylphosphonate (DMMP), and other vapor species. in order to conduct remote sensing using Raman, a fiber optic probe, was developed. lie probe permits the excitation and collection of Raman spectra over >50 m of optical fiber without interference from scattering originating within the fibers themselves, previously a serious problem with this approach. Spectral analysis has been conducted with small spectrographs, some of them palm-sized. Special Raman filters based on holographic optical elements were developed for this purpose, removing all vestiges of the primary Raman excitation light before introducing the scattered Raman light into the spectrograph. Several spectrograph configurations were examined, including a novel Echelle design which enables better than 1 cm-1