Zhao Huan, Zheng Chuantao, Pi Mingquan, Liang Lei, Song Fang, Zhang Yu, Wang Yiding, Tittel Frank K
State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, China.
State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, China.
Front Chem. 2022 Aug 23;10:953684. doi: 10.3389/fchem.2022.953684. eCollection 2022.
Portable or even on-chip detection of methane (CH) is significant for environmental protection and production safety. However, optical sensing systems are usually based on discrete optical elements, which makes them unsuitable for the occasions with high portability requirement. In this work, we report on-chip silicon-on-insulator (SOI) waveguide CH sensors at 3.291 μm based on two measurement schemes including direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). In order to suppress noise, Kalman filter was adopted in signal processing. By optimizing the waveguide cross-section structure, an etch depth of 220 nm was selected with an experimentally high power confinement factor (PCF) of 23% and a low loss of only 0.71 dB/cm. A limit of detection (LoD) of 155 parts-per-million (ppm) by DAS and 78 ppm by WMS at an averaging time of 0.2 s were obtained for a 2 cm-long waveguide sensor. Compared to the chalcogenide (ChG) waveguide CH sensors at the same wavelength, the reported sensor reveals the minimum waveguide loss and the lowest LoD. Therefore the SOI waveguide sensor has the potential of on-chip gas sensing in the mid-infrared (MIR) waveband.
便携式甚至芯片级的甲烷（CH₄）检测对于环境保护和生产安全具有重要意义。然而，光学传感系统通常基于离散光学元件，这使得它们不适用于对便携性要求较高的场合。在这项工作中，我们报道了基于两种测量方案（包括直接吸收光谱法（DAS）和波长调制光谱法（WMS））的3.291μm波长的绝缘体上硅（SOI）波导CH₄传感器。为了抑制噪声，在信号处理中采用了卡尔曼滤波器。通过优化波导横截面结构，选择了220nm的蚀刻深度，实验测得的高功率限制因子（PCF）为23%，低损耗仅为0.71dB/cm。对于一个2cm长的波导传感器，在平均时间为0.2s时，DAS的检测限（LoD）为155ppm，WMS的检测限为78ppm。与相同波长的硫系化物（ChG）波导CH₄传感器相比，所报道的传感器具有最小的波导损耗和最低的检测限。因此，SOI波导传感器在中红外（MIR）波段具有芯片级气体传感的潜力。
