Portable and cost-effective gas sensors are gaining demand for a number of environmental, biomedical, and industrial applications, yet current devices are confined into specialized labs and cannot be extended to general use. Here, we demonstrate a part-per-billion-sensitive refractive index gas sensor on a photonic chip based on silicon nitride waveguides functionalized with a mesoporous silica top-cladding layer. Low-concentration chemical vapors are detected by monitoring the output spectral pattern of an integrated unbalanced Mach-Zehnder interferometer having one coated arm exposed to the gas vapors. We retrieved a limit of detection of 65 ppb, 247 ppb, and 1.6 ppb for acetone, isopropyl alcohol, and ethanol, respectively. Our on-chip refractive index sensor provides, to the best of our knowledge, an unprecedented limit of detection for low gas concentrations based on photonic integrated circuits. As such, our results herald the implementation of compact, portable, and inexpensive devices for on-site and real-time environmental monitoring and medical diagnostics.

中文翻译：

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具有功能化氮化硅光子电路的超灵敏折射率气体传感器

便携式且具有成本效益的气体传感器对许多环境，生物医学和工业应用都有需求，但当前的设备仅限于专门的实验室，不能扩展到一般用途。在这里，我们展示了基于氮化硅波导的光子芯片上具有百万分之几的折射率气体传感器，该氮化硅波导具有介孔二氧化硅顶部覆层。通过监视集成的不平衡马赫曾德尔干涉仪的输出光谱图来检测低浓度的化学蒸汽，该不平衡Mach-Zehnder干涉仪的一根涂层臂暴露在气体蒸汽中。我们对丙酮，异丙醇和乙醇的检出限分别为65 ppb，247 ppb和1.6 ppb。据我们所知，我们的片上折射率传感器可提供：基于光子集成电路的低气体浓度检测的前所未有的极限。因此，我们的结果预示着将为现场和实时环境监测以及医学诊断提供紧凑，便携式和廉价的设备。