Carbon dioxide absorption spectroscopy with a mid-infrared silicon photonic waveguide

• Published in: Optics letters 2020-01, Vol.45 (1), p.109
• Main Authors: Ottonello-Briano, Floria, Errando-Herranz, Carlos, Rödjegård, Henrik, Martin, Hans, Sohlström, Hans, Gylfason, Kristinn B.
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Agricultural wastes; Carbon dioxide; Carbon dioxide absorption; Circuits; Consumer applications; Detection; Electromagnetic absorption; Environmental Monitoring; gas sensor; Gas sensors; High selectivity; Human wastes; Infrared devices; Infrared radiation; integrated optics; Light absorption; Lithography; MEMS; mid-IR; Optical measuring instruments; Optical waveguides; Photonic circuits; Photonic devices; Photonic waveguides; Photonics; Selectivity; Silicon on insulator technology; Silicon photonics; Silicon substrates; Silicon waveguide; Silicon-on-insulator substrates; waveguide
• ISSN: 0146-9592; 1539-4794; 1539-4794
• DOI: 10.1364/OL.45.000109

Carbon dioxide ( C O 2 ) is a gas vital for life on Earth. It is also a waste product of human activities and is widely used in agriculture and industry. Its accurate sensing is therefore of great interest. Optical sensors exploiting the mid-infrared light absorption of C O 2 provide high selectivity, but their large size and high cost limit their use. In this Letter, we demonstrate C O 2 gas sensing at 4.2 µm wavelength using an integrated silicon waveguide, featuring a sensitivity to C O 2 of 44% that of free-space sensing. The suspended waveguide is fabricated on a silicon-on-insulator substrate by a single-lithography-step process, and we route it into a mid-infrared photonic circuit for on-chip-referenced gas measurements. Its demonstrated performance and its simple and scalable fabrication make our waveguide ideal for integration in miniaturized C O 2 sensors for distributed environmental monitoring, personal safety, and medical and high-volume consumer applications.