| Abstract
| - A novel integrated acoustooptic tunable filter (IAOTF) hasbeen developed. This tunable filter is based on theBragginteractions between waveguide and surface acousticwaves. Compared to (bulk) AOTF, its advantagesincludeall-fiber construction, smaller size, narrower spectralresolution (1.7 nm), higher diffraction efficiency (37%),and lower rf power requirement (150 mW). A relativelynarrow spectral tuning range (about 80 nm) is the onlydrawback for this integrated tunable filter. However,thisdisadvantage was overcome by judiciously using the filterfor measurements in which its tuning range is coincidentwith the light source and also with absorption bands ofanalytes. In fact, an all-fiber, compact,high-throughputnear-infrared spectrophotometer has been successfullyconstructed by synergistic use of this integrated AOTF andthe erbium-doped fiber amplifier (EDFA), which has beenshown to provide high intensity and wide spectral bandwidth in the near-infrared region from 1500 to 1600 nm.This spectral region is particularly useful for thedetermination of samples which have O−H and/or N−Hgroups. The all-fiber nature, compactness, highthroughput, and high sensitivity of this spectrophotometer makeit particularly suitable for on-line and real-timedetectionof trace gases in hostile environments, including leakdetection of monomethylhydrazine (at a limit of detectionof 191 ppm), which is often used as the hypergolicpropellant for the space shuttle thruster systems.
|
