Liu Zhiwei, Zheng Chuantao, Chen Chen, Li Yafei, Xie Hongtao, Ren Qiang, Wang Yiding, Tittel Frank K
Opt Express. 2019 Feb 18;27(4):5598-5609. doi: 10.1364/OE.27.005598.
For deep-sea natural gas hydrate exploration, highly sensitive detection of the dissolved gas in seawater near the seabed is significant because it requires the sensor system to be small in size, low in power consumption, and high in sensitivity. A mid-infrared sensor system was developed to detect dissolved carbon dioxide (CO) in sea-water, while employing a 4319 nm continuous-wave interband cascade laser (ICL) and a multi-pass gas cell (MPGC) with a 29.8 m optical path length. A compact rectilinear optical structure was proposed by using the free-space-emitting ICL and tunable laser absorption spectroscopy (TLAS). This leads to a minimized sensor size and a simple optical alignment for deep-sea operation. A strong CO absorption line, located at 2315.19 cm and a weak 2315.28 cm line and at a low pressure of 40 Torr, was targeted for low- and high-concentration CO detection within a concentration range of 0-1000 parts per billion by volume (ppbv) and 0-40 parts per million by volume (ppmv), respectively. The limit of detection (LoD) was assessed to be 0.72 ppbv at an averaging time of 2 s, and the response time was measured to be ~30 s at a flow rate of ~180 standard cubic centimeters per minute (sccm). Deployment of the CO sensor combined with a gas-liquid separator was carried out for the CO detection in the gas extracted from water, which validated the reported sensor system's potential application for deep-sea natural gas hydrate exploration.
对于深海天然气水合物勘探而言，对海床附近海水中溶解气体进行高灵敏度检测意义重大，因为这要求传感器系统体积小、功耗低且灵敏度高。开发了一种中红外传感器系统来检测海水中的溶解二氧化碳（CO），该系统采用了波长为4319 nm的连续波带间级联激光器（ICL）和光程长度为29.8 m的多程气室（MPGC）。通过使用自由空间发射的ICL和可调谐激光吸收光谱技术（TLAS），提出了一种紧凑的直线光学结构。这使得传感器尺寸最小化，并为深海作业提供了简单的光学对准方式。针对浓度范围分别为0至1000体积十亿分比（ppbv）和0至40体积百万分比（ppmv）的低浓度和高浓度CO检测，选取了位于2315.19 cm的强CO吸收线以及位于2315.28 cm的弱吸收线，且压力为40 Torr。在平均时间为2 s时，检测限（LoD）评估为0.72 ppbv，在流速约为每分钟180标准立方厘米（sccm）时，响应时间测量为约30 s。结合气液分离器部署了CO传感器，用于检测从水中提取的气体中的CO，这验证了所报道的传感器系统在深海天然气水合物勘探中的潜在应用。
