研究目的
To present a photonic gas sensor concept based on silicon waveguides using infrared evanescent field absorption, specifically designed for CO2 sensing at a wavelength of λ = 4.26 μm.
研究成果
The study successfully demonstrated the use of sub-wavelength silicon strip waveguides for evanescent gas sensing, with the lowest intrinsic losses of 3.98 dB/cm and an evanescent field ratio in the range of 14%–16%. Future work will focus on improving the waveguide sensing structures and integrating a source and a detector for a fully integrated sensor setup.
研究不足
The study faced challenges such as the lack of reliable literature data for the extinction coefficients of the materials used in the mid-infrared range around 4.26 μm, and the measurement of intrinsic losses was challenging due to the sensitivity of the transmitted intensity to the fiber position.
1：Experimental Design and Method Selection:
The study involved designing silicon waveguides for CO2 sensing using finite-element simulations and fabricating the structures with mass production processes.
2：Sample Selection and Data Sources:
Polysilicon strip waveguides of various lengths were used to characterize intrinsic losses, and a strip waveguide meander was used for gas measurements.
3：List of Experimental Equipment and Materials:
A quantum cascade laser (QCL) was used as a mid-infrared radiation source, and optical fibers, IR detectors, a reference transmission cell, and a custom gas mixer were part of the setup.
4：Experimental Procedures and Operational Workflow:
The intrinsic losses were determined using an approach related to the cutback method, and quantitative CO2 measurements were conducted to estimate the evanescent field ratio.
5：Data Analysis Methods:
The Beer-Lambert law was used to model the power transmitted through the strip waveguide, and ANOVA was performed to analyze the influence of Si3N4 layer thickness on intrinsic losses.
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