Photonic Gas Sensor Using a Silicon Strip Waveguide

Abstract

Abstract:Sensing of gases is a promising area for applications of photonic systems operating in the mid-infrared spectral range. We present an infrared evanescent-field absorption gas sensor based on a silicon strip waveguide, which was specifically designed for CO2 sensing. We discuss finite element simulations that were used to design the strip waveguide and furthermore present experimental data of quantitative CO2 measurements with the devised structures. The first demonstrator device detects concentrations down to 5000 ppm CO2 which is the workplace exposure limit in most jurisdictions.

Silicon Waveguide Sensors for Carbon Dioxide Gas Sensing in the Mid-Infrared Region

“…The proposed gas sensor structures consist of the silicon slot waveguides as the core waveguide on the substrate of sapphire for CO2 monitoring, based on the absorption at 4.23 µ m. The FDTD (finite-difference time domain) method is used to simulate and analyze the performance of the sensor. Supposing the fundamental TE mode of the light source propagating along the z-axis, TM is not selected as it will cause a higher loss [23]. The height of the silicon waveguide is 1.00 µ m. The higher value of η leads to a stronger interaction between CO2 gas and the light.…”

“…The FDTD (finite-difference time domain) method is used to simulate and analyze the performance of the sensor. Supposing the fundamental TE mode of the light source propagating along the z-axis, TM is not selected as it will cause a higher loss [23]. The height of the silicon waveguide is 1.00 µm.…”

“…Most of the sensing chips are composed of silicon material as the core layer, and conventional cladding layer materials including silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), and sapphire (Al 2 O 3 ) [22][23][24]. A high refractive index difference between the core and cladding layer generates a strong evanescent field at the interface of the very small waveguide.…”