The ability to probe the molecular fundamental or overtone (high harmonics) vibrations is fundamental to modern healthcare monitoring techniques and sensing technologies since it provides information about the molecular structure. However, since the absorption cross section of molecular vibration overtones is much smaller compared to the absorption cross section of fundamental vibrations, their detection is challenging. Here, a silicon nanostrip rib waveguide structure is proposed for label-free on-chip overtone spectroscopy in near-infrared (NIR). Utilizing the large refractive index contrast (Δn > 2) between the silicon core of the waveguide and the silica substrate, a broadband NIR lightwave can be efficiently guided. We show that the sensitivity for chemical detection is increased by more than 3 orders of magnitude when compared to the evanescent-wave sensing predicted by the numerical model. This spectrometer distinguished several common organic liquids such as N-methylaniline and aniline precisely without any surface modification to the waveguide through the waveguide scanning over the absorption dips in the NIR transmission spectra. Planar NIR Si nanostrip waveguide is a compact sensor that can provide a platform for accurate chemical detection. Our NIR Si nanostrip rib waveguide device can enable the development of sensors for remote, on-site monitoring of chemicals.

中文翻译：

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用于纳米片上宽带分子泛音光谱的Si纳米带光波导

探测分子基本或泛音（高谐波）振动的能力是现代医疗保健监测技术和传感技术的基础，因为它提供了有关分子结构的信息。但是，由于分子振动泛音的吸收截面与基本振动的吸收截面相比要小得多，因此检测它们具有挑战性。在此，提出了一种硅纳米带肋波导结构，用于近红外（NIR）中的无标签芯片上泛音光谱学。利用大的折射率对比（Δn> 2）在波导的硅芯和二氧化硅基板之间，可以有效地引导宽带NIR光波。我们表明，与数值模型预测的e逝波检测相比，化学检测的灵敏度提高了3个数量级以上。该光谱仪通过在NIR透射光谱中的吸收谱上进行扫描，精确区分了几种常见的有机液体，例如N-甲基苯胺和苯胺，而对波导没有任何表面修饰。平面NIR Si纳米带状波导是一种紧凑型传感器，可以为精确的化学检测提供平台。我们的NIR Si纳米带肋波导器件可以实现传感器的开发，用于对化学品进行远程，现场监控。