Reddy Karthik, Fan Xudong
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
Opt Express. 2012 Jan 16;20(2):966-71. doi: 10.1364/OE.20.000966.
We develop a versatile, self-referenced composite Fabry-Pérot (FP) sensor and the corresponding detection scheme for rapid and precise measurement of vapors. The composite FP vapor sensor is formed by etching two juxtaposed micron-deep wells, with a precisely controlled offset in depth, on a silicon wafer. The wells are then coated with a vapor sensitive polymer and the reflected light from each well is detected by a CMOS imager. Due to its self-referenced nature, the composite FP sensor is able to extract the change in thickness and refractive index of the polymer layer upon exposure to analyte vapors, thus allowing for accurate vapor quantitation regardless of the polymer thickness, refractive index, and light incident angle and wavelength. Theoretical analysis is first performed to elucidate the underlying detection principle, followed by experimental demonstration at two different incident angles showing rapid and consistent measurement of the polymer changes when the polymer is exposed to three different analytes at various concentrations. The vapor detection limit is found to be on the order of a few pico-grams (~100 ppb).
我们开发了一种通用的、自参考复合法布里-珀罗（FP）传感器以及相应的检测方案，用于快速、精确地测量蒸汽。复合FP蒸汽传感器是通过在硅片上蚀刻两个并列的微米深阱形成的，阱的深度有精确控制的偏移。然后在阱上涂覆对蒸汽敏感的聚合物，并通过CMOS成像器检测来自每个阱的反射光。由于其自参考特性，复合FP传感器能够在暴露于分析物蒸汽时提取聚合物层厚度和折射率的变化，从而无论聚合物的厚度、折射率、光入射角和波长如何，都能进行准确的蒸汽定量。首先进行理论分析以阐明潜在的检测原理，随后在两个不同入射角进行实验演示，结果表明当聚合物暴露于三种不同浓度的分析物时，能够快速且一致地测量聚合物的变化。发现蒸汽检测限约为几皮克（~100 ppb）。
