On-chip mid-infrared silicon-on-insulator waveguide methane sensor using two measurement schemes at 3.291 μm

Huan Zhao; Chuantao Zheng; Mingquan Pi; Lei Liang; Fang Song; Yu Zhang; Yiding Wang; Frank K Tittel

doi:10.3389/fchem.2022.953684

On-chip mid-infrared silicon-on-insulator waveguide methane sensor using two measurement schemes at 3.291 μm

Front Chem. 2022 Aug 23:10:953684. doi: 10.3389/fchem.2022.953684. eCollection 2022.

Authors

Huan Zhao¹, Chuantao Zheng¹, Mingquan Pi¹, Lei Liang², Fang Song¹, Yu Zhang¹, Yiding Wang¹, Frank K Tittel³

Affiliations

¹ State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, China.
² State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, China.
³ Department of Electrical and Computer Engineering, Rice University, Houston, TX, United States.

Abstract

Portable or even on-chip detection of methane (CH₄) 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 CH₄ 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 CH₄ 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.

Keywords: SOI waveguide sensor; direct absorption spectroscopy; kalman filter; methane sensing; wavelength modulation spectroscopy.