Reflected path enhanced absorbance in an integrated photonic sensor
Reflected path enhanced absorbance in an integrated photonic sensor
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DOI：
10.1117/12.2664033
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发表时间：
2023-06
期刊：
影响因子：
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通讯作者：
Jianhao Shen;Daniel Donnelly;S. Chakravarty
中科院分区：
文献类型：
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作者：
Jianhao Shen;Daniel Donnelly;S. Chakravarty
光子集成电路中的逝去波传感器已被证明可用于气体传感应用。虽然一些方法依赖于某些聚合物的独特响应来检测特定气体，但吸收光谱根据其独特的振动特征来识别任何气体。根据Beer-Lambert原理，芯片上气体吸收的灵敏度依赖于敏感区域的长度、与被分析气体的光学重叠积分以及具有基本振动特征的波长处的吸收截面。在光子器件中，通过将缝隙波导限制与光子晶体慢光效应相结合，增强了光学模式与分析物的重叠。虽然吸收截面是气体的特性，但感测区域的长度受芯片上的可用面积和限制最小信噪比的波导传播损耗的限制。在本文中，我们证明了在相同几何长度的吸收传感波导中，通过引入反射环镜，可以使吸收光程增加一倍。通过2×2多模干涉(MMI)功分器，来自波导的光被分成两路，每路都带有慢光光子晶体波导。每条路径由环镜终止，该环镜使光沿传感臂返回其路径，从而使光与分析物相互作用的光路长度加倍。给出了在干涉构型中提高相位灵敏度和吸光度灵敏度的结果。
Evanescent wave sensors in photonic integrated circuits have been demonstrated for gas sensing applications. While some methods rely on the distinctive response of certain polymers for sensing specific gases, absorption spectroscopy identifies any gas uniquely from their unique vibration signatures. Based on the Beer-Lambert principle, the sensitivity of absorption by a gas on chip relies on the length of the sensing region, the optical overlap integral with the analyte gas and the absorption cross-section at the wavelength with the fundamental vibration signature. The overlap of the optical mode with the analyte has been enhanced in photonic devices by combining slot waveguide confinements with photonic crystal slow light effects. While the absorption cross-section is a property of the gas, the length of the sensing region is limited by the available area on a chip and waveguide propagation losses that limit the minimum signal to noise ratio. In this paper, we show that by incorporating reflecting loop mirrors, the absorption path length can be doubled for the same geometric length of the absorption sensing waveguide. Light from a waveguide is split into two paths, each with a slow light photonic crystal waveguide, by a 2×2 multimode interference (MMI) power splitter. Each path is terminated by a loop mirror that causes the light to retrace its path back down the sensing arms thereby doubling the optical path length over which light interacts with the analyte. Results on the enhancement of phase sensitivity and absorbance sensitivity in the interferometric configuration are presented.