Mid-infrared auto-correction on-chip waveguide gas sensor based on 2f/1f wavelength modulation spectroscopy.

Area of Science:

• Optical Engineering
• Spectroscopy
• Chemical Sensing

Background:

• On-chip direct absorption spectroscopy (DAS) is common but susceptible to noise.
• Second harmonic (2f) wavelength modulation spectroscopy (WMS) improves performance but is sensitive to optical power fluctuations.

Purpose of the Study:

• To develop a mid-infrared auto-correction on-chip gas sensor.
• To mitigate the impact of optical power variation on gas detection accuracy.
• To enhance the performance of on-chip gas sensing.

Main Methods:

• Implementation of a 2f/1f WMS technique for auto-correction.
• Utilizing a chalcogenide waveguide (10 mm length) for methane detection.
• Developing an integrated system for real-time optical power compensation.

Main Results:

• Achieved a limit of detection of 0.031% for methane (CH4).
• Reduced maximum relative concentration error by approximately 5.6 times compared to 2f WMS.
• Demonstrated measurement error ≤2% across a 30°C temperature range.

Conclusions:

• The auto-correction 2f/1f WMS sensor significantly improves accuracy and stability.
• This method reduces reliance on complex manual calibration for on-chip gas sensing.
• The developed sensor is suitable for high-accuracy integrated gas sensing applications.