LITES-Based Sensitive CO₂ Detection Using 2 μm Diode Laser and Self-Designed 9.5 kHz Quartz Tuning Fork

Area of Science:

• Spectroscopy
• Laser Technology
• Sensor Development

Background:

• Accurate carbon dioxide (CO2) monitoring is crucial for environmental and industrial applications.
• Existing CO2 sensors face limitations in detection limits and performance.
• Light-induced thermoelastic spectroscopy (LITES) offers a promising non-dispersive technique for gas sensing.

Purpose of the Study:

• To develop and characterize a novel CO2 sensor based on LITES.
• To investigate the impact of a self-designed low-frequency trapezoidal-head Quartz Tuning Fork (QTF) on sensor performance.
• To compare the performance of the novel sensor with a commercial QTF-based system.

Main Methods:

• Utilized a 2 μm diode laser targeting the strongest CO2 absorption line at 2004.01 nm.
• Employed a self-designed low-frequency trapezoidal-head QTF with a resonant frequency of 9464.18 Hz and Q-factor of 12,133.56.
• Performed Allan variance analysis to determine the minimum detection limit (MDL).

Main Results:

• The CO2-LITES sensor with the self-designed QTF exhibited excellent linear response to CO2 concentration.
• Achieved an initial minimum detection limit (MDL) of 46.08 ppm.
• Improved MDL to 3.59 ppm with a 100s averaging time, a 4.7-fold enhancement over the commercial QTF sensor (16.85 ppm).

Conclusions:

• The self-designed low-frequency trapezoidal-head QTF significantly enhances CO2-LITES sensor performance.
• The developed sensor offers a superior MDL and improved sensitivity compared to conventional QTF-based sensors.
• This technology presents a significant advancement for high-performance CO2 sensing applications.