Mid-infrared Integrated Photonic Platforms for On-chip Optical Gas Sensing

QC 20260504

Abstract

Integrated photonics has emerged as a rapidly advancing field,attracting significant attention for its ability to enable high-speed,energy-efficient, and scalable optical systems. Its unique capabilities make it a prevailing technology in a wide range of emerging applications, including next-generation telecommunications, artificial intelligence infrastructure, quantum computing, and miniaturized environmental sensing platforms. Among the various optical spectral ranges,the mid-infrared range (2-20 µm) holds particular significance for environmental sensing, owing to its rich rotational–vibrational molecular absorption features. Mid-infrared integrated photonics offers advantages over traditional optical gas sensors, including compact size, improved energy efficiency, and the ability to integrate multiple optical functionalities and multi-gas detection on a single platform. Despite the rapid progress of integrated photonics in the near-infrared range, mainly driven by telecommunications applications, the development of mid-infrared integrated photonic platforms has proceeded at a comparatively slower pace.

This thesis aims to develop mid-infrared integrated photonic platforms for gas sensing applications, with a focus on extending the operational wavelength range, integrating light sources and photodetectors, and ensuring compatibility with existing silicon photonics infrastructure. The key achievements of this thesis include: (1) the development of silicon-on-insulator and germanium-on-silicon integrated photonic platforms; (2) the integration of graphene-based photothermoelectric photodetectors and thermal emitters; and (3) the demonstration of integrated gas sensing for carbon dioxide, methane,and ethanol. The developed platforms exhibit low propagation losses by leveraging the excellent fabrication quality and unique waveguide designs, while preserving high sensitivity for gas sensing applications. The use of graphene for integrating photodetectors and light sources enables the development of a fully integrated mid-infrared photonic platform based on a single active material, offering broad spectral coverage for diverse gas sensing applications. This thesis establishes a foundation for advancing mid-infrared photonic technologies and exploring emerging applications in this spectral range. It paves the way toward high-performance, scalable, and versatile integrated photonic platforms for gas sensing applications. In addition, the realized platforms can be extended to additional mid-infrared applications, such as free-space optical communication and nonlinear optical studies.

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