Tran C D, Gao G H
Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, USA.
Anal Chem. 1997 Apr 1;69(7):1461-4. doi: 10.1021/ac960919u.
A novel integrated acoustooptic tunable filter (IAOTF) has been developed. This tunable filter is based on the Bragg interactions between waveguide and surface acoustic waves. Compared to (bulk) AOTF, its advantage include all-fiber construction, smaller size, narrower spectral resolution (1.7 nm), higher diffraction efficiency (37%), and lower rf power requirement (150 mW). A relatively narrow spectral tuning range (about 80 nm) is the only drawback for this integrated tunable filter. However, this disadvantage was overcome by judiciously using the filter for measurements in which its tuning range is coincident with the light source and also with absorption bands of analytes. In fact, an all-fiber, compact, high-throughput near-infrared spectrophotometer has been successfully constructed by synergistic use of this integrated AOTF and the erbium-doped fiber amplifier (EDFA), which has been shown to provide high intensity and wide spectral band-width in the near-infrared region from 1500 to 1600 nm. This spectral region is particularly useful for the determination of samples which have O-H and/or N-H groups. The all-fiber nature, compactness, high throughput, and high sensitivity of this spectrophotometer make it particularly suitable for on-line and real-time detection of trace gases in hostile environments, including leak detection of monomethylhydrazine (at a limit of detection of 191 ppm), which is often used as the hypergolic propellant for the space shuttle thruster systems.
一种新型集成声光可调滤波器（IAOTF）已被研制出来。这种可调滤波器基于波导与表面声波之间的布拉格相互作用。与（体）声光可调滤波器相比，其优点包括全光纤结构、尺寸更小、光谱分辨率更窄（1.7纳米）、衍射效率更高（37%）以及射频功率要求更低（150毫瓦）。相对较窄的光谱调谐范围（约80纳米）是这种集成可调滤波器的唯一缺点。然而，通过明智地将该滤波器用于其调谐范围与光源以及分析物吸收带相重合的测量中，这一缺点得以克服。实际上，通过协同使用这种集成声光可调滤波器和掺铒光纤放大器（EDFA），已成功构建了一台全光纤、紧凑、高通量的近红外分光光度计，该放大器在1500至1600纳米的近红外区域已被证明能提供高强度和宽光谱带宽。这个光谱区域对于测定含有O - H和/或N - H基团的样品特别有用。该分光光度计的全光纤特性、紧凑性、高通量和高灵敏度使其特别适用于在恶劣环境中对痕量气体进行在线和实时检测，包括对常用于航天飞机推进系统自燃推进剂的一甲肼的泄漏检测（检测限为191 ppm）。
