Thanks to the unique molecular fingerprints in the mid-infrared spectral region, absorption spectroscopy in this regime has attracted widespread attention in recent years. Contrary to commercially available infrared spectrometers, which are limited by being bulky and cost-intensive, laboratory-on-chip infrared spectrometers can offer sensor advancements including raw sensing performance in addition to utilization such as enhanced portability. Several platforms have been proposed in the past for on-chip ethanol detection. However, selective sensing with high sensitivity at room temperature has remained a challenge. Here, we experimentally demonstrate an on-chip ethyl alcohol sensor based on a holey photonic crystal waveguide on silicon on insulator-based photonics sensing platform offering an enhanced photoabsorption thus improving sensitivity. This is achieved by designing and engineering an optical slow-light mode with a high group-index of n g = 73 and a strong localization of the modal power in analyte, enabled by the photonic crystal waveguide structure. This approach includes a codesign paradigm that uniquely features an increased effective path length traversed by the guided wave through the to-be-sensed gas analyte. This PIC-based lab-on-chip sensor is exemplary, spectrally designed to operate at the center wavelength of 3.4 μm to match the peak absorbance for ethanol. However, the slow-light enhancement concept is universal offering to cover a wide design-window and spectral ranges towards sensing a plurality of gas species. Using the holey photonic crystal waveguide, we demonstrate the capability of achieving parts per billion levels of gas detection precision. High sensitivity combined with tailorable spectral range along with a compact form-factor enables a new class of portable photonic sensor platforms when integrated with quantum cascade laser and detectors.

中文翻译：

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迈向使用中红外光子晶体波导的芯片实验室超灵敏乙醇检测

得益于中红外光谱区中独特的分子指纹，近年来这种方法中的吸收光谱法引起了广泛的关注。与市售的红外光谱仪相比，后者受到体积和成本密集的限制，与之相反，片上实验室红外光谱仪除了提供诸如便携性之类的利用率外，还可以提供包括原始传感性能在内的传感器进步。过去已经提出了几种用于片上乙醇检测的平台。然而，在室温下具有高灵敏度的选择性感测仍然是一个挑战。在这里，我们实验性地展示了一个基于片上乙醇传感器，该传感器基于基于绝缘体的光子传感平台上的硅上的有孔光子晶体波导，可提供增强的光吸收能力，从而提高了灵敏度。这是通过设计和设计具有ng = 73的高组指数和光子晶体波导结构所能实现的分析物的模态功率的强局部化的光学慢光模式来实现的。该方法包括一个代码符号范例，该范例独特地具有被引导波穿过待感测的气体分析物所经过的有效路径长度增加的特征。这种基于PIC的芯片实验室传感器是示例性的，在光谱上设计为在3.4μm的中心波长下运行，以匹配乙醇的峰值吸收率。然而，慢光增强概念是普遍提供的，以覆盖广泛的设计窗口和光谱范围，以检测多种气体。使用多孔光子晶体波导，我们证明了达到十亿分之几的气体检测精度等级的能力。