Real-Time Tracking of Carbon Dioxide Concentration Using an Optical Microsphere Resonator Sensor

Area of Science:

• Optical Sensing
• Resonator Technology
• Environmental Monitoring

Background:

• Whispering gallery mode (WGM) resonators are optical sensors for gaseous environments.
• Their resonant properties (wavelength, amplitude, Q factor) enable rapid, stable monitoring.
• High sensitivity, low cost, and small size make them suitable for disposable, extreme-environment sensors.

Purpose of the Study:

• To compare the spectral response of different diameter WGM resonators to carbon dioxide (CO2) and nitrogen (N2) mixtures.
• To characterize and quantify the effect of environmental temperature on spectral shifts.
• To demonstrate real-time tracking and recovery capabilities of the resonator sensor.

Main Methods:

• Spectral analysis of resonator responses to varying gas concentrations (CO2, N2).
• Quantification of thermo-optic effects on spectral shifts.
• Real-time monitoring of gas concentration changes.

Main Results:

• Observed spectral shifting and broadening of cavity resonance near 1550 nm.
• Quantified temperature-induced spectral shifts due to the thermo-optic effect.
• Demonstrated sensor's ability to track and recover gas concentrations in real-time.

Conclusions:

• WGM resonators show potential for sensitive, real-time gas sensing.
• Understanding and decoupling environmental factors like temperature is crucial for accurate measurements.
• The sensor exhibits promising tracking and recovery capabilities for dynamic gas environments.