Atmospheric-level carbon dioxide gas sensing using low-loss mid-IR silicon waveguides

Area of Science:

• Photonics and Materials Science
• Environmental Sensing Technology

Background:

• Growing concern over indoor/outdoor air quality links to health.
• Carbon dioxide (CO2) sensors are vital for monitoring ventilation and pollution.
• Existing CO2 sensors lack scalability and adequate performance for atmospheric levels.

Purpose of the Study:

• To develop a scalable, high-performance CO2 gas sensor.
• To demonstrate a novel integrated optical waveguide for CO2 detection.
• To achieve low detection limits for atmospheric CO2 monitoring.

Main Methods:

• Designed and fabricated a suspended silicon waveguide on a 150 mm SOI platform.
• Utilized standard optical lithography for mass manufacturing potential.
• Operated the sensor at a 4.2 µm wavelength for CO2 detection.

Main Results:

• Achieved clear detection of 500 ppm CO2 at 1s integration time.
• Extrapolated a 1σ detection limit of 73 ppm at 61s integration time.
• Demonstrated low propagation loss (2.20 dB/cm) with a unique waveguide design.

Conclusions:

• The proposed waveguide sensor offers a low CO2 detection limit.
• Compatibility with high-volume production via standard lithography.
• Significant potential for applications in fossil fuel monitoring and indoor air quality management.