We report a new method of accurately measuring the mid-infrared absorption of fluid analytes using on-chip waveguides that allows measurements to be referenced for noise and drift reduction whilst using only a single external detector. A silicon-on-insulator waveguide circuit integrated with a microfluidic channel is made in which a pair of switches alternate light between an evanescent absorption sensor waveguide and a reference waveguide at a rate of a few kHz, thus allowing low frequency common noise components to be removed from the measurement, and leading to a reduction in the noise floor by a factor of 11 compared to a simple waveguide absorption sensor. The device was verified by using it to detect an Isopropyl alcohol (IPA) absorption peak at a wavelength of 3.77 µm.

中文翻译：

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使用硅波导实现低噪声自参考中红外吸收传感的集成开关电路


我们报告了一种使用片上波导精确测量流体分析物的中红外吸收的新方法，该方法允许在仅使用单个外部检测器的同时为减少噪声和漂移提供测量参考。制作了与微流体通道集成的绝缘体上硅波导电路，其中一对开关以几kHz的速率在倏逝吸收传感器波导和参考波导之间交替光，从而允许低频公共噪声分量从测量中去除，与简单的波导吸收传感器相比，本底噪声降低了 11 倍。通过使用该装置检测波长 3.77 µm 处的异丙醇 (IPA) 吸收峰来验证该装置。