Midinfrared (2.5–25 μm) spectroscopy is an ideal tool for identifying chemicals in a nondestructive manner. The traditional platform is a Fourier transform infrared (FTIR) spectrometer, but this is too bulky, expensive, and power-hungry for many applications. There is therefore a growing demand for small, lightweight, and cost-effective microspectrometers for use in the field. One emerging platform is the filter-array detector-array microspectrometer. It pairs a broadband detector array with a thin and rigid array of spectral filters to offer a robust, compact platform for real-time in situ sensing. However, most demonstrations have only focused on identifying a single chemical against a null sample, even though many applications would involve multianalyte detection. In this work, we show a rare attempt at simultaneously tracking multiple analytes with a metasurface filter-array microspectrometer. The metasurface consists of periodic lattices of subwavelength circular apertures in an aluminum layer to create an array of bandpass filters. The filter array is imaged with an off-the-shelf microbolometer via a reverse-lens imaging setup to simultaneously monitor the concentration of ethanol and methanol in gasoline. This represents an important application of fuel quality monitoring. Chemometric models (PLS and SVR) are trained and tested on gasoline blends with ethanol and methanol contents, both ranging from 0% to 20% v/v. A support vector machine regression (SVR) model with a cubic kernel was found to have the lowest combined prediction errors. The root-mean-square-error of prediction (RMSEP) for ethanol and methanol are 1.23% and 1.84% v/v; the corresponding pseudounivariate limit of detection is found to be 4.22% and 6.86% v/v, respectively. This work takes the emerging field of metasurface-based mid-infrared spectrometers from single- to multianalyte detection, thereby considerably expanding their range of potential applications.

中文翻译：

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使用基于超表面的中红外微型光谱仪进行多分析物检测


中红外 （2.5–25 μm） 光谱法是以无损方式鉴定化学品的理想工具。传统平台是傅里叶变换红外 （FTIR） 光谱仪，但对于许多应用来说，它过于笨重、昂贵且耗电。因此，对用于现场的小型、轻便且经济高效的微型光谱仪的需求不断增长。一个新兴的平台是滤光片阵列探测器阵列微型光谱仪。它将宽带探测器阵列与薄而刚性的光谱滤光片阵列配对，为实时原位传感提供强大、紧凑的平台。然而，大多数演示仅侧重于从零样品中鉴定单一化学品，尽管许多应用涉及多分析物检测。在这项工作中，我们展示了一种罕见的尝试，即使用超表面滤光片阵列微型光谱仪同时跟踪多种分析物。超表面由铝层中亚波长圆形孔径的周期性晶格组成，以形成带通滤光片阵列。使用现成的微测辐射热计通过反向镜头成像装置对过滤器阵列进行成像，以同时监测汽油中乙醇和甲醇的浓度。这是燃油质量监测的一个重要应用。化学计量学模型（PLS 和 SVR）在乙醇和甲醇含量为 0% 至 20% v/v 的汽油混合物上进行训练和测试。发现具有三次核的支持向量机回归 （SVR） 模型具有最低的组合预测误差。乙醇和甲醇的预测均方根误差 （RMSEP） 分别为 1.23% 和 1.84% v/v;发现相应的假单变量检测限分别为 4.22% 和 6.86% V/V。 这项工作将基于超表面的中红外光谱仪的新兴领域从单一分析物检测发展到多分析物检测，从而大大扩展了它们的潜在应用范围。