Ultra-sensitive refractive index gas sensor with functionalized silicon nitride photonic circuits

Giuseppe Antonacci,Jeroen Goyvaerts,Bernhard Lendl,Roel Baets,Bettina Baumgartner,Haolan Zhao

doi:10.1063/5.0013577

Giuseppe Antonacci, Jeroen Goyvaerts + Show 4 more

Open Access

https://doi.org/10.1063/5.0013577

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Journal: APL Photonics	Publication Date: Aug 1, 2020
Citations: 32	License type: cc-by

Affiliation: Ghent University, TU Wien

Abstract

Portable and cost-effective gas sensors are gaining demand for a number of environmental, biomedical, and industrial applications, yet current devices are confined into specialized labs and cannot be extended to general use. Here, we demonstrate a part-per-billion-sensitive refractive index gas sensor on a photonic chip based on silicon nitride waveguides functionalized with a mesoporous silica top-cladding layer. Low-concentration chemical vapors are detected by monitoring the output spectral pattern of an integrated unbalanced Mach-Zehnder interferometer having one coated arm exposed to the gas vapors. We retrieved a limit of detection of 65 ppb, 247 ppb, and 1.6 ppb for acetone, isopropyl alcohol, and ethanol, respectively. Our on-chip refractive index sensor provides, to the best of our knowledge, an unprecedented limit of detection for low gas concentrations based on photonic integrated circuits. As such, our results herald the implementation of compact, portable, and inexpensive devices for on-site and real-time environmental monitoring and medical diagnostics.

Highlights

E (SiN) platform offers an excellent solution for sensing as a consequence of its broadband transparency window into the visible domain and the generally lower propagation losses compared to the SOI platform.6 Given its versatility and the possibility to integrate multiple optical functionalities, the silicon nitride (SiN) platform has already enabled the implementation of several sensing devices for a variety of applications including biosensing,7–9 Raman spectroscopy,10–12 and absorption spectroscopy.13 More recently, the SiN platform has further seen adoption for gas sensing
We demonstrate a part-per-billion-sensitive refractive index gas sensor on a photonic chip based on silicon nitride waveguides functionalized with a mesoporous silica top-cladding layer
Similar approaches based on integrated Mach-Zehnder interferometer (MZI) realized with SOI and SiN platforms have been demonstrated with different types of coatings and waveguide structures to detect organic solvents,15 ethanol vapors,16 and methane,17 reporting a limit of detection (LOD) in the order of tens of ppm

Summary

Introduction

E (SiN) platform offers an excellent solution for sensing as a consequence of its broadband transparency window into the visible domain and the generally lower propagation losses compared to the SOI platform.6 Given its versatility and the possibility to integrate multiple optical functionalities, the SiN platform has already enabled the implementation of several sensing devices for a variety of applications including biosensing,7–9 Raman spectroscopy,10–12 and absorption spectroscopy.13 More recently, the SiN platform has further seen adoption for gas sensing. We demonstrate a part-per-billion-sensitive refractive index gas sensor on a photonic chip based on silicon nitride waveguides functionalized with a mesoporous silica top-cladding layer.

Results

Conclusion