Key Laboratory for Information Science of Electromagnetic Waves (MoE), Fudan University, Shanghai 200433, China.
Sensors (Basel). 2019 Apr 10;19(7):1698. doi: 10.3390/s19071698.
A new gas absorption module, the substrate-embedded hollow waveguide (eHWG) model, is proposed. It consists of a substrate with a curved channel and a hollow waveguide. The hollow waveguide is curved into the channel and works as a gas absorption cell as well as a transmission medium for mid-infrared light. Owing to the low loss property of the hollow waveguide, the signal-to-noise ratio (SNR) was improved for the sensing system. A polycarbonate (PC) base tube was used to obtain flexibility in the fabrication of the hollow waveguide. A silver (Ag) layer and a silver iodide (AgI) layer were inner-coated to ensure a low loss property at the fingerprint wavelength of methane gas. A sensing system was established using a Fourier transform infrared spectrometer (FTIR), an external detector, and an eHWG. Experimental investigations were carried on the sensing performance of eHWGs with various channel shapes. Comparison studies were made on eHWGs embedded with Ag-coated or Ag- and AgI-coated hollow waveguides. The Ag- and AgI-coated hollow waveguides with inner diameters of 0.7, 1.4, and 2.0 mm were used in the eHWGs. The large bore waveguide had low loss but high bending additional loss. The large bore waveguide had a low detection limit due to high coupling efficiency with the light source. A limit of detection (LOD) as low as 2.7 ppm was attained for the system using the eHWG with the long and large bore waveguide.
提出了一种新型的气体吸收模块，即基底嵌入式中空波导（eHWG）模型。它由带有弯曲通道的基底和中空波导组成。中空波导弯曲成通道，既作为气体吸收池，又作为中红外光的传输介质。由于中空波导的低损耗特性，提高了传感系统的信噪比（SNR）。采用聚碳酸酯（PC）基管来获得中空波导制造的灵活性。内涂银（Ag）层和碘化银（AgI）层，以确保甲烷气体指纹波长的低损耗特性。使用傅里叶变换红外光谱仪（FTIR）、外部探测器和 eHWG 建立了传感系统。对具有各种通道形状的 eHWG 的传感性能进行了实验研究。对嵌入有涂银或涂银和碘化银中空波导的 eHWG 进行了比较研究。在 eHWG 中使用了内径为 0.7、1.4 和 2.0mm 的涂银和碘化银中空波导。大口径波导具有低损耗但高弯曲附加损耗。由于与光源的耦合效率高，大口径波导具有较低的检测极限。使用带有长而大口径波导的 eHWG，系统的检测极限（LOD）低至 2.7ppm。
